Joins Colt on Android Sniper System

<div dir="ltr" style="text-align: left;" trbidi="on"><div class="separator" style="clear: both; text-align: center;"><a href="http://s19.postimg.org/irfx7ghjn/DSC_2600_A.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://s19.postimg.org/irfx7ghjn/DSC_2600_A.jpg" /></a></div><br /><span style="color: red;"><span style="font-family: Georgia,"Times New Roman",serif;"><span style="font-size: small;"><b>General Dynamics Canada and Colt Canada are working together to plug Colt’s Sniper Weapon & Observer Reconnaissance Devices system into the battlefield network.</b></span></span></span><br /><span style="color: red;"><span style="font-family: Georgia,"Times New Roman",serif;"><span style="font-size: small;"><b>Colt showed off the SWORD system earlier this year at the Association of the United States Army’s annual meeting. The Android-based system joins weapon-mounted surveillance and targeting devices with ruggedized smartphone-like technology, Colt officials maintain.</b></span></span></span><br /><br /><span style="color: red;"><span style="font-family: Georgia,"Times New Roman",serif;"><span style="font-size: small;"><b>The SWORD system is designed to bring situational-awareness information directly to the solider via his weapon and it will be offered as an alternative to radio-centric individual soldier systems. Based on commercial components, the SWORD system provides power, data and navigation infrastructure within the weapon, including GPS and inertial navigation for GPS-denied situations, Colt officials maintain.</b></span></span></span><br /><br /><br /><br /><br /><a name="more"></a><br /><br /><blockquote class="tr_bq"><i>SWORD makes sense as an integrated soldier system,” Jeff MacLeod, general manager of Colt Canada, said in a recent press release. “By combining modern smartphone technology with weapon-mounted scopes and laser rangefinders, soldiers have all the information they need, literally at their fingertips. SWORD is not about simply delivering a computer or a display to soldiers; it delivers an entirely new capability centered on the rifle.</i></blockquote><br /><div class="separator" style="clear: both; text-align: center;"><span style="font-size: small;"><b><a href="http://s19.postimg.org/kknf9is43/DSC_2592.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://s19.postimg.org/kknf9is43/DSC_2592.jpg" /></a></b></span></div><br /><div style="border: medium none; color: black; overflow: hidden; text-align: left; text-decoration: none;"></div><div style="border: medium none; color: black; overflow: hidden; text-align: left; text-decoration: none;"><div style="border: medium none; color: black; overflow: hidden; text-align: left; text-decoration: none;"><br /><br /><b><span style="font-family: Georgia,"Times New Roman",serif;"><span style="font-size: small;"><span style="color: red;">General Dynamics Canada and Colt Canada are working together to plug Colt’s Sniper Weapon & Observer Reconnaissance Devices system into the battlefield network.</span></span></span></b><br /><b><span style="font-family: Georgia,"Times New Roman",serif;"><span style="font-size: small;"><span style="color: red;">Colt showed off the SWORD system earlier this year at the Association of the United States Army’s annual meeting. The Android-based system joins weapon-mounted surveillance and targeting devices with ruggedized smartphone-like technology, Colt officials maintain.</span></span></span></b><br /><b><span style="font-family: Georgia,"Times New Roman",serif;"><span style="font-size: small;"><span style="color: red;">The SWORD system is designed to bring situational-awareness information directly to the solider via his weapon and it will be offered as an alternative to radio-centric individual soldier systems. Based on commercial components, the SWORD system provides power, data and navigation infrastructure within the weapon, including GPS and inertial navigation for GPS-denied situations, Colt officials maintain.</span></span></span></b><br /><br /><span style="color: blue;"><b><span style="font-family: Georgia,"Times New Roman",serif;"><span style="font-size: small;"> Maybe GD and Colt will have more luck.</span></span></b></span><br /><br /><blockquote class="tr_bq"><span style="color: blue;"><b><span style="font-family: Georgia,"Times New Roman",serif;"><span style="font-size: small;"> </span></span></b></span><i>Cooperation between Colt and General Dynamics Canada builds on the strengths of both companies,” says David Ibbetson, vice president, General Dynamics C4 Systems International. “Colt has worldwide expertise in developing and delivering rifles, while General Dynamics has the networking experience needed to connect individual soldiers. The combined solution gives soldiers the smartphone capability they have been asking for in the form of an Android-networked rifle.</i></blockquote><br /><div style="border: medium none; color: black; overflow: hidden; text-align: left; text-decoration: none;"><br /></div></div></div><div style="border: medium none; color: black; overflow: hidden; text-align: left; text-decoration: none;"><br /></div></div>

Android gun Heartbeat Sensor Rifle Rifle Sniper Sniper Sniper System Tech Joins Colt on Android Sniper System

General Dynamics Canada and Colt Canada are working together to plug Colt’s Sniper Weapon & Observer Reconnaissance Devices system into...

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CPU Cache Flushing Fallacy

<div dir="ltr" style="text-align: left;" trbidi="on"><br /><div dir="ltr" style="text-align: left;" trbidi="on"><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></a><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></a><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></a><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></a><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></a><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></a><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></a><a href="http://www.blogger.com/P36-HIW-CPU.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;" target="_blank"></a><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><br /></a><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><br /></a><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"></a><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"></a><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"></a><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"></a><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"></a><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"></a><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"></a><a href="http://www.blogger.com/P36-HIW-CPU.jpg" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;" target="_blank"></a>Even from highly experienced technologists I often hear talk about how certain operations cause a CPU cache to "flush".  This seems to be illustrating a very common fallacy about how CPU caches work, and how the cache sub-system interacts with the execution cores.  In this article I will attempt to explain the function CPU caches fulfil, and how the cores, which execute our programs of instructions, interact with them.  For a concrete example I will dive into one of the latest Intel x86 server CPUs.  Other CPUs use similar techniques to achieve the same ends.<br /><br /><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"></a><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"></a><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"></a><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"></a><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"></a><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"></a><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"></a><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"></a><a href="http://www.blogger.com/P36-HIW-CPU.jpg" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;" target="_blank"></a>Most modern systems that execute our programs are shared-memory multi-processor systems in design.  A shared-memory system has a single memory resource that is accessed by 2 or more independent CPU cores.  Latency to main memory is highly variable from 10s to 100s of nanoseconds.  Within 100ns it is possible for a 3.0GHz CPU to process up to 1200 instructions.  Each Sandy Bridge core is capable of retiring up to 4 instructions-per-cycle (IPC) in parallel.  CPUs employ cache sub-systems to hide this latency and allow them to exercise their huge capacity to process instructions.  Some of these caches are small, very fast, and local to each core; others are slower, larger, and shared across cores.  Together with registers and main-memory, these caches make up our non-persistent memory hierarchy.</div><div dir="ltr" style="text-align: left;" trbidi="on"><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://www.blogger.com/P36-HIW-CPU.jpg" style="margin-left: 1em; margin-right: 1em;" target="_blank"></a></div> Next time you are developing an important algorithm, try pondering that a cache-miss is a lost opportunity to have executed ~500 CPU instructions!  This is for a single-socket system, on a multi-socket system you can effectively double the lost opportunity as memory requests cross socket interconnects.<br /><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></a><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></a><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></a><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></a><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></a><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></a><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></a><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></a><a href="http://www.blogger.com/P36-HIW-CPU.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;" target="_blank"></a><br /><span style="font-family: Arial, Helvetica, sans-serif; font-size: large;"><b>Memory Hierarchy</b></span><br /><br /><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody><tr><td style="text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="http://www.blogger.com/P36-HIW-CPU.jpg" style="margin-left: 1em; margin-right: 1em;" target="_blank"></a></div><div class="separator" style="clear: both; text-align: center;"><a href="http://www.blogger.com/blogger.g?blogID=7321614453975088586" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"></a></div> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEix6YX78BHNI7oZIBQIihs6uu1-EmN82lnp3L9u8ilI3ikWib5khyphenhyphenvzK4oX3YGAKjaCOBU8TeWBAUqRVmWSOlFNT9D_Yvxn256geU_kfXCUdTV7_-RhYgC8ipiv6bcux82iKjCaRM9uKpY/s1600/MemoryHeirarchy.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="441" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEix6YX78BHNI7oZIBQIihs6uu1-EmN82lnp3L9u8ilI3ikWib5khyphenhyphenvzK4oX3YGAKjaCOBU8TeWBAUqRVmWSOlFNT9D_Yvxn256geU_kfXCUdTV7_-RhYgC8ipiv6bcux82iKjCaRM9uKpY/s640/MemoryHeirarchy.png" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Figure 1.</td></tr></tbody></table><br /><br /><a name="more"></a>For the circa 2012 Sandy Bridge E class servers our memory hierarchy can be decomposed as follows:<br /><ol style="text-align: left;"><li><b>Registers</b>: Within each core are separate register files containing 160 entries for integers and 144 floating point numbers.  These registers are accessible within a single cycle and constitute the fastest memory available to our execution cores.  Compilers will allocate our local variables and function arguments to these registers.  Compilers allocate to subset of registers know as the <a href="http://en.wikipedia.org/wiki/X86#x86_registers">architectural registers</a>, then the hardware expands on these as it runs instructions in parallel and out-of-order.  Compilers are aware of out-of-order and parallel execution ability for given processor, and order instruction streams and register allocation to take advantage of this.  When <a href="http://en.wikipedia.org/wiki/Hyper-threading">hyperthreading</a> is enabled these registers are shared between the co-located hyperthreads.</li><li><b>Memory Ordering Buffers (MOB)</b>: The MOB is comprised of a 64-entry load and 36-entry store buffer.  These buffers are used to track in-flight operations while waiting on the cache sub-system as instructions get executed out-of-order.  The store buffer is a fully associative queue that can be searched for existing store operations, which have been queued when waiting on the L1 cache.  These buffers enable our fast processors to run without blocking while data is transferred to and from the cache sub-system.  When the processor issues reads and writes they can can come back out-of-order.  The MOB is used to disambiguate the load and store ordering for compliance to the published <a href="http://en.wikipedia.org/wiki/Memory_model_(programming)">memory model</a>.  Instructions are executed out-of-order in addition to our loads and stores that can come back out-of-order from the cache sub-system.  These buffers enable an ordered view of the world to be re-constructed for what is expected according to the memory model.</li><li><b>Level 1 Cache</b>: The L1 is a core-local cache split into separate 32K data and 32K instruction caches.  Access time is 3 cycles and can be hidden as instructions are <a href="http://en.wikipedia.org/wiki/Pipelining">pipelined</a> by the core for data already in the L1 cache.</li><li><b>Level 2 Cache</b>: The L2 cache is a core-local cache designed to buffer access between the L1 and the shared L3 cache.  The L2 cache is 256K in size and acts as an effective queue of memory accesses between the L1 and L3.  L2 contains both data and instructions.  L2 access latency is 12 cycles.  </li><li><b>Level 3 Cache</b>: The L3 cache is shared across all cores within a socket.  The L3 is split into 2MB segments each connected to a ring-bus network on the socket.  Each core is also connected to this ring-bus.  Addresses are hashed to segments for greater throughput.  Latency can be up to 38 cycles depending on cache size.  Cache size can be up to 20MB depending on the number of segments, with each additional hop around the ring taking an additional cycle.  The L3 cache is inclusive of all data in the L1 and L2 for each core on the same socket.  This inclusiveness, at the cost of space, allows the L3 cache to intercept requests thus removing the burden from private core-local L1 & L2 caches.</li><li><b>Main Memory</b>: DRAM channels are connected to each socket with an average latency of ~65ns for socket local access on a full cache-miss.  This is however extremely variable, being much less for subsequent accesses to columns in the same row buffer, through to significantly more when queuing effects and memory refresh cycles conflict.  4 memory channels are aggregated together on each socket for throughput, and to hide latency via  <a href="http://en.wikipedia.org/wiki/Pipelining">pipelining</a> on the independent memory channels.</li><li><b>NUMA</b>: In a multi-socket server we have <a href="http://en.wikipedia.org/wiki/Non-Uniform_Memory_Access">non-uniform memory access</a>.  It is non-uniform because the required memory maybe on a remote socket having an additional 40ns hop across the <a href="http://en.wikipedia.org/wiki/QPI">QPI</a> bus.  Sandy Bridge is a major step forward for 2-socket systems over Westmere and Nehalem.  With Sandy Bridge the QPI limit has been raised from 6.4GT/s to 8.0GT/s, and two lanes can be aggregated thus eliminating the bottleneck of the previous systems.  For Nehalem and Westmere the QPI link is only capable of ~40% the bandwidth that could be delivered by the memory controller for an individual socket.  This limitation made accessing remote memory a choke point.  In addition, the QPI link can now forward pre-fetch requests which previous generations could not.</li></ol><div><b><span style="font-family: Arial, Helvetica, sans-serif; font-size: large;">Associativity Levels</span></b></div><div><br /></div><div>Caches are effectively hardware based hash tables.  The hash function is usually a simple masking of some low-order bits for cache indexing.  Hash tables need some means to handle a collision for the same slot.  The associativity level is the number of slots, also known as ways or sets, which can be used to hold a hashed version of an address.  Having more levels of associativity is a trade off between storing more data vs. power requirements and time to search each of the ways.</div><div><br /></div><div>For Sandy Bridge the L1D and L2 are 8-way associative, the L3 is 12-way associative.</div><div><br /></div><span style="font-family: Arial, Helvetica, sans-serif; font-size: large;"><b>Cache Coherence</b></span><br /><br />With some caches being local to cores, we need a means of keeping them coherent so all cores can have a consistent view of memory.  The cache sub-system is considered the "source of truth" for mainstream systems.  If memory is fetched from the cache it is never stale; the cache is the master copy when data exists in both the cache and main-memory.  This style of memory management is known as <a href="http://www.webopedia.com/TERM/W/write_back_cache.html">write-back</a> whereby data in the cache is only written back to main-memory when the cache-line is evicted because a new line is taking its place.  An x86 cache works on blocks of data that are 64-bytes in size, known as a <a href="http://en.wikipedia.org/wiki/CPU_cache#Cache_Entries">cache-line</a>.  Other processors can use a different size for the cache-line.  A larger cache-line size reduces effective latency at the expense of increased bandwidth requirements.<br /><br />To keep the caches coherent the cache controller tracks the state of each cache-line as being in one of a finite number of states.  The protocol Intel employs for this is <a href="http://www.realworldtech.com/common-system-interface/5/">MESIF</a>, AMD employs a variant know as <a href="http://en.wikipedia.org/wiki/MOESI_protocol">MOESI</a>.  Under the MESIF protocol each cache-line can be in 1 of the 5 following states:<br /><ol style="text-align: left;"><li><b>Modified</b>: Indicates the cache-line is dirty and must be written back to memory at a later stage.  When written back to main-memory the state transitions to Exclusive.</li><li><b>Exclusive</b>: Indicates the cache-line is held exclusively and that it matches main-memory.  When written to, the state then transitions to Modified.  To achieve this state a Read-For-Ownership (RFO) message is sent which involves a read plus an invalidate broadcast to all other copies.</li><li><b>Shared</b>: Indicates a clean copy of a cache-line that matches main-memory.</li><li><b>Invalid</b>: Indicates an unused cache-line.</li><li><b>Forward</b>: Indicates a specialised version of the shared state i.e. this is the designated cache which should respond to other caches in a NUMA system.</li></ol>To transition from one state to another, a series of messages are sent between the caches to effect state changes.  Previous to <a href="http://en.wikipedia.org/wiki/Nehalem_(microarchitecture)">Nehalem</a> for Intel, and <a href="http://en.wikipedia.org/wiki/Opteron">Opteron</a> for AMD, this cache coherence traffic between sockets had to share the memory bus which greatly limited scalability.  These days the memory controller traffic is on a separate bus.  The Intel QPI, and AMD <a href="http://en.wikipedia.org/wiki/HyperTransport">HyperTransport</a>, buses are used for cache coherence between sockets.<br /><br />The cache controller exists as a module within each L3 cache segment that is connected to the on-socket ring-bus network.  Each core, L3 cache segment, QPI controller, memory controller, and integrated graphics sub-system are connected to this ring-bus.  The ring is made up of 4 independent lanes for: <i>request</i>, <i>snoop</i>, <i>acknowledge</i>, and 32-bytes <i>data </i>per cycle.  The L3 cache is inclusive in that any cache-line held in the L1 or L2 caches is also held in the L3.  This provides for rapid identification of the core containing a modified line when snooping for changes.  The cache controller for the L3 segment keeps track of which core could have a modified version of a cache-line it owns.<br /><br />If a core wants to read some memory, and it does not have it in a Shared, Exclusive, or Modified state; then it must make a read on the ring bus.  It will then either be read from main-memory if not in the cache sub-systems, or read from L3 if clean, or snooped from another core if Modified.  In any case the read will never return a stale copy from the cache sub-system, it is guaranteed to be coherent.<br /><br /><b><span style="font-family: Arial, Helvetica, sans-serif; font-size: large;">Concurrent Programming</span></b><br /><br />If our caches are always coherent then why do we worry about visibility when writing concurrent programs?  This is because within our cores, in their quest for ever greater performance, data modifications can appear out-of-order to other threads.  There are 2 major reasons for this.<br /><br />Firstly, our compilers can generate programs that store variables in registers for relatively long periods of time for performance reasons, e.g. variables used repeatedly within a loop.  If we need these variables to be visible across cores then the updates must not be register allocated.  This is achieved in C by qualifying a variable as "<span style="font-family: Courier New, Courier, monospace;">volatile</span>".  Beware that C/C++ <span style="font-family: Courier New, Courier, monospace;">volatile</span> is inadequate for telling the compiler not to reorder other instructions.  For this you need memory fences/barriers.<br /><br />The second major issue with ordering we have to be aware of is a thread could write a variable and then, if it reads it shortly after, could see the value in its store buffer which may be older than the latest value in the cache sub-system.  This is never an issue for algorithms following the <a href="http://mechanical-sympathy.blogspot.co.uk/2011/09/single-writer-principle.html">Single Writer Principle</a>.  The store buffer also allows a load instruction to get ahead of an older store and is thus an issue for the likes of the <a href="http://en.wikipedia.org/wiki/Dekker%27s_algorithm">Dekker</a> and <a href="http://en.wikipedia.org/wiki/Peterson%27s_algorithm">Peterson</a> lock algorithms.  To overcome these issues, the thread must not let a sequential consistent load get ahead of the sequentially consistent store of the value in the local store buffer.  This can be achieved by issuing a fence instruction.  The write of a <span style="font-family: Courier New, Courier, monospace;">volatile</span> variable in Java, in addition to never being register allocated, is accompanied by a full fence instruction.  This fence instruction on x86 has a significant performance impact by preventing progress on the issuing thread until the store buffer is drained.  Fences on other processors can have more efficient implementations that simply put a marker in the store buffer for the search boundary, e.g. the Azul Vega does this.<br /><br />If you want to ensure memory ordering across Java threads when following the Single Writer Principle, and avoid the store fence, it is possible by using the <span style="font-family: Courier New, Courier, monospace;">j.u.c.Atomic(Int|Long|Reference).lazySet()</span> method, as opposed to setting a <span style="font-family: Courier New, Courier, monospace;">volatile</span> variable.<br /><br /><b><span style="font-family: Arial, Helvetica, sans-serif; font-size: large;">The Fallacy</span></b><br /><br />Returning to the fallacy of "flushing the cache" as part of a concurrent algorithm.  I think we can safely say that we never "flush" the CPU cache within our user space programs.  I believe the source of this fallacy is the need to flush, mark or drain to a point, the store buffer for some classes of concurrent algorithms so the latest value can be observed on a subsequent load operation.  For this we require a memory ordering fence and not a cache flush.<br /><br />Another possible source of this fallacy is that L1 caches, or the <a href="http://en.wikipedia.org/wiki/Translation_lookaside_buffer">TLB</a>, may need to be flushed based on address indexing policy on a context switch.  ARM, previous to ARMv6, did not use address space tags on TLB entries thus requiring the whole L1 cache to be flushed on a context switch.  Many processors require the L1 instruction cache to be flushed for similar reasons, in many cases this is simply because instruction caches are not required to be kept coherent. The bottom line is, context switching is expensive and a bit off topic, so in addition to the cache pollution of the L2, a context switch can also cause the TLB and/or L1 caches to require a flush.  Intel x86 processors require only a TLB flush on context switch.</div></div>

Cache Computer CPU Memory Work CPU Cache Flushing Fallacy

Even from highly experienced technologists I often hear talk about how certain operations cause a CPU cache to "flush".  This seem...

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How To Create Your Own Run Commands

<div dir="ltr" style="text-align: left;" trbidi="on"><div class="post-content-right"></div>There is no doubt that <b>Microsoft Windows</b> is the most widely used <b>operating system</b> in all parts of the world. Apart from being simple to use, it is quite rich in features as well, which makes our lives quite easy.<br />The Run command available on Windows operating system is one such power packed feature that lets you to open a document or an application instantly with the help of just <b>1 command</b>. So, rather than clicking several icons or using multiple commands, you can use the Run command to open any program or document instantly.<br /><br /><br /><a href="http://s19.postimg.org/vol8g6lzn/crete_your_own1.png"><img alt="crete your own run command" class="size-full wp-image-95 aligncenter" height="210" src="http://www.smarttricks.net/wp-content/uploads/2013/09/crete-your-own1.png" width="410" /></a><br /><br />But, do you know how to create your own run commands? Well, it is really easy, which involves just few steps. Through this article, I will help you understand how to access your favorite applications by creating <b>custom Run commands.</b><br /><b>Open Run Command</b><br /><b></b>Before I show you how to create your own Run commands, let’s take a quick look on how to open Run Command. First of all, you need to open the Run window by just pressing the Windows Key along with the R key, i.e. Windows + R. Now, you have to type the name of the program that you desire to open up or execute. Unfortunately, not all programs can be accessed through this method. So, let me show you how to create Run commands that do not come as inbuilt commands.<br /><hr /><h3 style="text-align: center;">Step to Be Followed</h3><hr /><h3 style="text-align: center;"></h3><b>Step 1.</b> The first step is to select the software or application for which you want to make custom Run command. For example, let us consider <b>Google Chrome</b> as the example here. Remember, you can choose any application other than which is already there in the Run command. <br /><hr /><br /><b>Step 2.</b> In the second step, right click on the desktop of your computer system and make a new shortcut.<br /><b>Right click > New > Shortcut</b><br /><hr /><br /><b>Step 3.</b> As you select the Shortcut option in the 2nd Step, it will open up a dialog box. And, the dialog box will ask you path of the application or software for which you want to create the Run command.<br /><hr /><br /><b>Step 4.</b> Now, you need to browse through the files and choose the one that shows “<b>chrome.exe</b>”. Well, it is quite obvious that all the executable files can be found in the C drive (or wherever the Operating System has been installed), inside the folder “<b>Program Files</b>”. For example, “<b>C:\Program Files\Google Chrome\chrome.exe</b>”<br /><hr /><br /><b>Step 5</b>. Once you are done with Step number 4, just click on “<b>Next</b>” button and simply provide a relative name to that shortcut. Remember, the same name will be used later in the Run command.<br />For example, “<b>GC</b>” for <b>Google Chrome</b><br /><hr /><br /><b>Step 6.</b> Now, click on the “<b>Finish</b>” button. Once it is done, an icon related to that application or software will show up on your computer’s screen. It means that the process of creating shortcut has been done successfully.<br /><hr /><br /><b>Step 7.</b> In this step, just cut and paste that recently made shortcut icon into your computer’s root drive, in its Windows folder.<br />For example, C:\ Windows , Make sure you are the administrator of the computer or have its password.<br /><hr /><br /><b>Step 8.</b> Now, you are done with the set up and can run the application through Run Command. Just go to Run and enter the keyword “<b>GC</b>”, and Google Chrome will begin executing.<br /><hr /><br /><div style="clear: both; font-size: 0px; height: 0px; line-height: 0px; margin: 0; padding: 0;">Post to Fac</div><div class="shr-publisher-40 shareaholic-show-on-load" style="height: 87px; margin-left: 160px; overflow: hidden;"><div class="shr-bookmarks shr-bookmarks-bg-shr" style="background: url("http://www.smarttricks.net/wp-content/plugins/sexybookmarks/images/share-knowledge.png") no-repeat scroll 0% 0% transparent; display: block; height: 100%; margin-left: 10px; overflow: hidden; padding: 35px 0px 0px 10px;"><ul class="shr-socials"><li class="shr-5 shareaholic" style="margin-left: 0px !important;"><a class="external" href="http://www.shareaholic.com/api/share/?title=How+To+Create+Your+Own+Run+Commands&link=http%3A%2F%2Fwww.smarttricks.net%2Fcreate-your-own-run-commands%2F&notes=&short_link=&shortener=shrlc&shortener_key=&v=1&apitype=1&apikey=8afa39428933be41f8afdb8ea21a495c&source=Shareaholic-Publishers&template=&service=5&ctype=" orig_title="Post to Facebook" rel="nofollow" target="_blank"></a><div class="shr-count"><div aria-hidden="true" class="shr-count-outline" style="left: 10px; top: -12px;"><br /></div><div aria-label="Number of times this webpage has been shared" class="shr-count-center" style="left: 10px; top: -11px;"><br /></div></div></li><li class="shr-7 shareaholic" style="margin-left: 0px !important;"><a class="external" href="http://www.blogger.com/null" orig_title="Post to Twitter" rel="nofollow" target="_blank">Post to Twitter</a><div class="shr-count"><div aria-hidden="true" class="shr-count-outline" style="left: 9px; top: -10px;">12</div><div aria-hidden="true" class="shr-count-outline" style="left: 10px; top: -10px;">12</div><div aria-hidden="true" class="shr-count-outline" style="left: 11px; top: -10px;">12</div><div aria-hidden="true" class="shr-count-outline" style="left: 9px; top: -11px;">12</div><div aria-hidden="true" class="shr-count-outline" style="left: 11px; top: -11px;">12</div><div aria-hidden="true" class="shr-count-outline" style="left: 9px; top: -12px;">12</div><div aria-hidden="true" class="shr-count-outline" style="left: 10px; top: -12px;">12</div><div aria-hidden="true" class="shr-count-outline" style="left: 11px; top: -12px;">12</div><div aria-label="Number of times this webpage has been shared" class="shr-count-center" style="left: 10px; top: -11px;">12</div></div></li><li class="shr-88 shareaholic" style="margin-left: 0px !important;"><a class="external" href="http://www.shareaholic.com/api/share/?title=How+To+Create+Your+Own+Run+Commands&link=http%3A%2F%2Fwww.smarttricks.net%2Fcreate-your-own-run-commands%2F&notes=&short_link=&shortener=shrlc&shortener_key=&v=1&apitype=1&apikey=8afa39428933be41f8afdb8ea21a495c&source=Shareaholic-Publishers&template=&service=88&ctype=" orig_title="Add to LinkedIn" rel="nofollow" target="_blank">Add to LinkedIn</a></li><li class="shr-304 shareaholic" style="margin-left: 0px !important;"><a class="external" href="http://www.shareaholic.com/api/share/?title=How+To+Create+Your+Own+Run+Commands&link=http%3A%2F%2Fwww.smarttricks.net%2Fcreate-your-own-run-commands%2F&notes=&short_link=&shortener=shrlc&shortener_key=&v=1&apitype=1&apikey=8afa39428933be41f8afdb8ea21a495c&source=Shareaholic-Publishers&template=&service=304&ctype=" orig_title="Post to Google+" rel="nofollow" target="_blank">Post to Google+</a></li><li class="shr-38 shareaholic" style="margin-left: 0px !important;"><a class="external" href="http://www.shareaholic.com/api/share/?title=How+To+Create+Your+Own+Run+Commands&link=http%3A%2F%2Fwww.smarttricks.net%2Fcreate-your-own-run-commands%2F&notes=&short_link=&shortener=shrlc&shortener_key=&v=1&apitype=1&apikey=8afa39428933be41f8afdb8ea21a495c&source=Shareaholic-Publishers&template=&service=38&ctype=" orig_title="Post to StumbleUpon" rel="nofollow" target="_blank">Post to StumbleUpon</a></li><li class="shr-313 shareaholic" style="margin-left: 0px !important;"><a class="external" href="http://www.shareaholic.com/api/share/?title=How+To+Create+Your+Own+Run+Commands&link=http%3A%2F%2Fwww.smarttricks.net%2Fcreate-your-own-run-commands%2F&notes=&short_link=&shortener=shrlc&shortener_key=&v=1&apitype=1&apikey=8afa39428933be41f8afdb8ea21a495c&source=Shareaholic-Publishers&template=&service=313&ctype=" orig_title="Send via Shareaholic Mail" rel="nofollow" target="_blank">Send via Shareaholic Mail</a></li><li class="shr-309 shareaholic" style="margin-left: 0px !important;"><a class="external" href="http://www.shareaholic.com/api/share/?title=How+To+Create+Your+Own+Run+Commands&link=http%3A%2F%2Fwww.smarttricks.net%2Fcreate-your-own-run-commands%2F&notes=&short_link=&shortener=shrlc&shortener_key=&v=1&apitype=1&apikey=8afa39428933be41f8afdb8ea21a495c&source=Shareaholic-Publishers&template=&service=309&ctype=" orig_title="Post to Pinterest" rel="nofollow" target="_blank">Post to Pinterest</a></li></ul></div></div></div>

command Custom Run Run Command windows How To Create Your Own Run Commands

There is no doubt that Microsoft Windows is the most widely used operating system in all parts of the world. Apart from being simple to us...

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Free Mobile Recharge - Inaugural Offer

<div dir="ltr" style="text-align: left;" trbidi="on"><div class="separator" style="clear: both; text-align: center;"><a href="http://adfoc.us/5820031762869" target="_blank"><img alt="Free Mobile Recharge" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEitz7zy465utNiFIZkAB9ZfHq-F8te6MQZFE709ALfm7_Ap1pMHqKu1sln3aKpLrVCXRdO32Dkeyn18qnc910WbzIvZp1f93JfZW-PjXlW4nJ2g4EHd8ykMTqpC-_zbNCJXR-K1v-GFKVw/s1600/free-mobile-recharge.png" title="Free Mobile Recharge" /></a> </div><div class="separator" style="clear: both; text-align: center;"><br /></div><div class="separator" style="clear: both; text-align: left;"> <a href="http://adfoc.us/5820031762869" target="_blank">Dudubu</a> is offering <a href="http://adfoc.us/5820031762869" target="_blank">free mobile recharge of <b>Rs.10/-</b></a> as an inaugural offer, register now and get free recharge of Rs.10 instantly.</div><br />You can register multiple accounts with different email ids and get your all mobile numbers recharged with Rs.10/- for free without paying. This free recharge offer has been started from 14th October 2013 and its still running on, so why leave this opportunity get your free recharge done now without paying.<br /><div style="text-align: center;"><a href="http://adfoc.us/5820031762869" target="_blank"><b><span style="font-size: x-large;">Recharge Now</span></b></a> </div><div class="separator" style="clear: both; text-align: center;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="http://adfoc.us/5820031762869" target="_blank"><img alt="Free Mobile Recharge Offer" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhR09kQSsObxq_jAQW6AT2sgiPr2-TCc1jRD7xU1pPSc0JVoTxL8Y4sZlZEgQYMGUU4Ew2156CO5vh5QXgleWzHiBOdL2t_FBDuSyLUx4938cJWHC8HdVo0fPSiZ4tAtzDiI7PAyrFnO3w/s1600/free-recharge.png" title="Free Mobile Recharge Offer" /></a> </div><div class="separator" style="clear: both; text-align: center;"><br /></div><div class="separator" style="clear: both; text-align: left;">You can recharge for free mobile operators like Aircel, Airtel, BSNL, Idea, Loop Mobile, MTNL Mumbai, MTS, Reliance CDMA, Reliance GSM, T24 Mobile, Tata Docomo CDMA, Tata Docomo GSM, Uninor, Videocon, Virgin GSM, Virgin CDMA, Vodafone.</div><br />Recharge your Mobile <a href="http://adfoc.us/5820031762869" target="_blank">now</a> for free by visiting below link. <br /><div class="separator" style="clear: both; text-align: left;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="http://adfoc.us/5820031762869" target="_blank"><b><span style="font-size: x-large;">Recharge Now</span></b></a></div><br /></div>

dudubu free Free Recharge Recharge Free Mobile Recharge - Inaugural Offer

  Dudubu is offering free mobile recharge of Rs.10/- as an inaugural offer, register now and get free recharge of Rs.10 instantly. You c...

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BBM™ from BlackBerry is now here for Android

<div dir="ltr" style="text-align: left;" trbidi="on"><div dir="ltr" style="text-align: left;" trbidi="on"><div dir="ltr" style="text-align: left;" trbidi="on"><h2 class="catbg" style="text-align: center;">  <span style="font-family: Georgia,"Times New Roman",serif;"><span style="color: red;"></span></span><span style="color: blue; text-decoration: blink;">BBM™ from BlackBerry is now here for Android</span></h2><h2 class="catbg" style="text-align: center;"><span style="color: blue; text-decoration: blink;"> </span></h2><h3 style="text-align: left;"><span style="font-family: Georgia,"Times New Roman",serif;"><span style="color: red;">The OFFICIAL version of BBM™ from BlackBerry is now here for Android. Get the free BBM app for the best way to stay connected with friends and family. Download it now. Chat with friends on Android, BlackBerry and iPhone:</span></span></h3><br /><br /><br /><span style="color: #741b47;"><span style="font-size: small;">• BBM is always on and always connected – no app to open</span></span><br /><span style="color: #741b47;"><span style="font-size: small;"><br />• Know when messages have been delivered (D’s) and read (R’s)</span></span><br /><span style="color: #741b47;"><span style="font-size: small;"><br />• Share photos, files, documents, voice notes and more</span></span><br /><span style="color: #741b47;"><span style="font-size: small;"><br />• See when contacts are responding to your message</span></span><br /><span style="color: #741b47;"><span style="font-size: small;"><br />• Emoticons for every mood and emotion let you express yourself BBM lets you protect your privacy. You control it:</span></span><br /><span style="color: #741b47;"><span style="font-size: small;"><br />• You chose how to share your information - BBM uses PINs instead of phone numbers or email addresses so that it's more private, and you always control who can contact you</span></span><br /><span style="color: #741b47;"><span style="font-size: small;"><br />• You chose your contacts – 2-way opt-in means you have control over who is able to messge you Chat and Share with many at once:</span></span><br /><span style="color: #741b47;"><span style="font-size: small;"><br />• Groups – BBM groups help you share pictures, lists, and appointments with group members. You can even be in a group with people who aren't part of your own BBM contact list.</span></span><br /><span style="color: #741b47;"><span style="font-size: small;"><br />• Multi-person chats – Invite multiple contacts to have a chat together.</span></span><br /><span style="color: #741b47;"><span style="font-size: small;"><br />• Broadcast messages – Send a message to multiple BBM contacts at one time. Create your own BBM profile:</span></span><br /><span style="color: #741b47;"><span style="font-size: small;"><br />• Post a profile picture using images, pictures or even animated pictures (GIFs).</span></span><br /><span style="color: #741b47;"><span style="font-size: small;"><br />• Update your status to let people know what you’re up to or how you feel Download BBM for free today. </span></span></div></div><h2 style="text-align: center;"><span style="color: purple;"><span style="font-size: x-large;"><a href="https://play.google.com/store/apps/details?id=com.bbm">Download Here</a></span></span> </h2></div>

Android Android APP Android Application APK app Application BBM BlackBerry Multi Platform BBM™ from BlackBerry is now here for Android

  BBM™ from BlackBerry is now here for Android   The OFFICIAL version of BBM™ from BlackBerry is now here for Android. Get the free BBM app ...

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Ghost keyboard Typing-Make Notepad type Automatically

<div dir="ltr" style="text-align: left;" trbidi="on">Hey guys , Today I am going to share with you a Short but Cool notepad trick. You can show it to your friends and surprise them. Basically it is a prank that you can do with anyone just for fun.<br /><br />This Process is Also known as “ <b><span style="text-decoration: blink;">Ghost Keyboard Typing</span></b> ”<br /><br /><br /><div class="separator" style="clear: both; text-align: center;"></div><div class="separator" style="clear: both; text-align: center;"></div><div class="separator" style="clear: both; text-align: center;"></div><div class="separator" style="clear: both; text-align: center;"><a href="http://zen-tek.blogspot.com/" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="301" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjAdWJc88AxkFUsPMqJjwd-JC_LpplvGWxcjnN-_pGPi6fUha67yty-zZZz4e0W4FyDBe2a7JRvvYH9zKu4g0aIyvhLx7JT6Eoo_cuuRL_dgtwSK2az0ikoIy2JuhfR_HVCcyASBsicFs9G/s640/ghost-keyboard-typing.jpg" width="400" /></a></div><hr /><h2 dir="ltr" style="text-align: center;">Just follow the simple steps to Learn the Prank</h2><h2 dir="ltr" style="text-align: center;"></h2><hr /><br /><a name="more"></a><br /><br /><br /><div dir="ltr" style="text-align: left;"><b>Step 1:</b> Right click on your desktop and select create new text document or simply Open Notepad.</div><div dir="ltr"><b>Step 2:</b> Exactly Copy the code given below and Paste it in notepad document that you have just created.<br /><br /></div><hr /><br /><blockquote class="tr_bq">set wshshell = wscript.CreateObject(“wScript.Shell”)<br />wshshell.run “Notepad”<br />wscript.sleep 400<br />wshshell.sendkeys “Z”<br />wscript.sleep 100<br />wshshell.sendkeys “E”<br />wscript.sleep 120<br />wshshell.sendkeys “N”<br />wscript.sleep 200<br />wshshell.sendkeys “-”<br />wscript.sleep 100<br />wshshell.sendkeys “T”<br />wscript.sleep 140<br />wshshell.sendkeys “E”<br />wscript.sleep 100<br />wshshell.sendkeys “K”<br />wscript.sleep 50<br />wshshell.sendkeys “.”<br />wscript.sleep 120<br />wshshell.sendkeys “B”<br />wscript.sleep 170<br />wshshell.sendkeys “L”<br />wscript.sleep 100<br />wshshell.sendkeys “O”<br />wscript.sleep 50<br />wshshell.sendkeys “G”<br />wscript.sleep 170<br />wshshell.sendkeys “S”<br />wscript.sleep 100<br />wshshell.sendkeys “P”<br />wscript.sleep 50<br />wshshell.sendkeys “O”<br />wscript.sleep 100<br />wshshell.sendkeys “T”<br />wscript.sleep 50<br />wshshell.sendkeys “.”<br />wscript.sleep 120<br />wshshell.sendkeys “C”<br />wscript.sleep 160<br />wshshell.sendkeys “O”<br />wscript.sleep 200<br />wshshell.sendkeys “M”<br />wscript.sleep 100</blockquote><hr /><br /><div dir="ltr"><b>Step 3:</b> Save the above code in Notepad file As ” <b>zentek.vbs</b> ” (Without Quotes ) but make sure  While saving this file select Save as type  ”<b>All files</b>” and extension must be <b>.vbs </b></div><div style="float: none; margin: 10px 0 10px 0; text-align: center;"><b> </b></div><b></b><br /><div dir="ltr"><b>Step 4:</b> Now double click on The saved File, You will see “<b>ZEN-TEK.BLOGSPOT.COM</b> ” will be typed  Automatically. Moreover  you can edit the Words In the above given Code with any desired words you want Notepad to type for you. <b>e.g. : MY FRIEND READING THIS IS FOOL.</b></div><div dir="ltr"><b></b></div><div dir="ltr"><b><br /></b></div><div dir="ltr"><b><br /></b></div><div dir="ltr"><b></b><b></b><br /><b></b></div><br /><div style="border: red solid 1px; padding: 5px;"><div style="text-align: center;"><span style="font-size: large; text-align: ceter;">IMPORTANT !!! </span></div><div dir="ltr" style="text-align: left;">While Double Clicking on the saved file if you see an error box like ” <b>line 1</b> ” and “<b>Char 37</b>” Then dont worry, Right click on <b style="color: red;">zentek.vbs</b> and click on edit,</div>Now delete all Double quotations ie : ”  and Type them all manually from your keyboard, save it and now you will have no errors.</div></div>

Automatic typing Script Fool Ghost Keybord keyboard keybord pank Script Trick Vbs Ghost keyboard Typing-Make Notepad type Automatically

Hey guys , Today I am going to share with you a Short but Cool notepad trick. You can show it to your friends and surprise them. Basically ...

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