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<span class="vector-toc-numb">5</span> <span>External links</span> </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" title="Table of Contents" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span 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data-feature-name="appearance-pinned" data-pinnable-element-id="vector-appearance" data-pinned-container-id="vector-appearance-pinned-container" data-unpinned-container-id="vector-appearance-unpinned-container" > <div class="vector-pinnable-header-label">Appearance</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-appearance.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-appearance.unpin">hide</button> </div> </div> </div> </nav> </div> </div> <div id="bodyContent" class="vector-body" aria-labelledby="firstHeading" data-mw-ve-target-container> <div class="vector-body-before-content"> <div class="mw-indicators"> </div> <div id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Performance-degrading usage pattern</div> <p>In <a href="/wiki/Computer_science" title="Computer science">computer science</a>, <b>false sharing</b> is a performance-degrading usage pattern that can arise in systems with distributed, <a href="/wiki/Cache_coherence" title="Cache coherence">coherent caches</a> at the size of the smallest resource block managed by the caching mechanism. When a system participant attempts to periodically access data that is not being altered by another party, but that data shares a cache block with data that <i>is</i> being altered, the caching protocol may force the first participant to reload the whole cache block despite a lack of logical necessity.<sup id="cite_ref-Patterson_2012_p._537_1-0" class="reference"><a href="#cite_note-Patterson_2012_p._537-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> The caching system is unaware of activity within this block and forces the first participant to bear the caching system overhead required by true shared access of a resource. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Multiprocessor_CPU_caches">Multiprocessor CPU caches</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=False_sharing&action=edit&section=1" title="Edit section: Multiprocessor CPU caches"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>By far the most common usage of this term is in modern <a href="/wiki/Multiprocessor" class="mw-redirect" title="Multiprocessor">multiprocessor</a> <a href="/wiki/CPU_cache" title="CPU cache">CPU caches</a>, where <a href="/wiki/Random_access_memory" class="mw-redirect" title="Random access memory">memory</a> is cached in <a href="/wiki/Cache_line" class="mw-redirect" title="Cache line">lines</a> of some small <a href="/wiki/Power_of_two" title="Power of two">power of two</a> <a href="/wiki/Word_(data_type)" class="mw-redirect" title="Word (data type)">word</a> size (e.g., 64 <a href="/wiki/Data_structure_alignment" title="Data structure alignment">aligned</a>, contiguous <a href="/wiki/Byte" title="Byte">bytes</a>). If two processors operate on independent data in the same <a href="/wiki/Memory_address" title="Memory address">memory address</a> region storable in a single line, the cache coherency mechanisms in the system may force the whole line across the <a href="/wiki/Bus_(computing)" title="Bus (computing)">bus</a> or interconnect with every data write, forcing memory stalls in addition to wasting system <a href="/wiki/Bandwidth_(computing)" title="Bandwidth (computing)">bandwidth</a>. In some cases, the elimination of false sharing can result in order-of-magnitude performance improvements.<sup id="cite_ref-Bolosky_2-0" class="reference"><a href="#cite_note-Bolosky-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> False sharing is an inherent artifact of automatically synchronized cache protocols and can also exist in environments such as distributed file systems or databases, but current prevalence is limited to RAM caches. </p> <div class="mw-heading mw-heading2"><h2 id="Example">Example</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=False_sharing&action=edit&section=2" title="Edit section: Example"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-highlight mw-highlight-lang-cpp mw-content-ltr" dir="ltr"><pre><span></span><span class="cp">#include</span><span class="w"> </span><span class="cpf"><iostream></span> <span class="cp">#include</span><span class="w"> </span><span class="cpf"><thread></span> <span class="cp">#include</span><span class="w"> </span><span class="cpf"><new></span> <span class="cp">#include</span><span class="w"> </span><span class="cpf"><atomic></span> <span class="cp">#include</span><span class="w"> </span><span class="cpf"><chrono></span> <span class="cp">#include</span><span class="w"> </span><span class="cpf"><latch></span> <span class="cp">#include</span><span class="w"> </span><span class="cpf"><vector></span> <span class="k">using</span><span class="w"> </span><span class="k">namespace</span><span class="w"> </span><span class="nn">std</span><span class="p">;</span> <span class="k">using</span><span class="w"> </span><span class="k">namespace</span><span class="w"> </span><span class="nn">chrono</span><span class="p">;</span> <span class="cp">#if defined(__cpp_lib_hardware_interference_size)</span> <span class="c1">// default cacheline size from runtime</span> <span class="k">constexpr</span><span class="w"> </span><span class="kt">size_t</span><span class="w"> </span><span class="n">CL_SIZE</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hardware_constructive_interference_size</span><span class="p">;</span> <span class="cp">#else</span> <span class="c1">// most common cacheline size otherwise</span> <span class="k">constexpr</span><span class="w"> </span><span class="kt">size_t</span><span class="w"> </span><span class="n">CL_SIZE</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">64</span><span class="p">;</span> <span class="cp">#endif</span> <span class="kt">int</span><span class="w"> </span><span class="nf">main</span><span class="p">()</span> <span class="p">{</span> <span class="w"> </span><span class="n">vector</span><span class="o"><</span><span class="n">jthread</span><span class="o">></span><span class="w"> </span><span class="n">threads</span><span class="p">;</span> <span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">hc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">jthread</span><span class="o">::</span><span class="n">hardware_concurrency</span><span class="p">();</span> <span class="w"> </span><span class="n">hc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hc</span><span class="w"> </span><span class="o"><=</span><span class="w"> </span><span class="n">CL_SIZE</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">hc</span><span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">CL_SIZE</span><span class="p">;</span> <span class="w"> </span><span class="k">for</span><span class="p">(</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">nThreads</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w"> </span><span class="n">nThreads</span><span class="w"> </span><span class="o"><=</span><span class="w"> </span><span class="n">hc</span><span class="p">;</span><span class="w"> </span><span class="o">++</span><span class="n">nThreads</span><span class="w"> </span><span class="p">)</span> <span class="w"> </span><span class="p">{</span> <span class="w"> </span><span class="c1">// synchronize beginning of threads coarse on kernel level</span> <span class="w"> </span><span class="n">latch</span><span class="w"> </span><span class="n">coarseSync</span><span class="p">(</span><span class="w"> </span><span class="n">nThreads</span><span class="w"> </span><span class="p">);</span> <span class="w"> </span><span class="c1">// fine synch via atomic in userspace</span> <span class="w"> </span><span class="kt">atomic_uint</span><span class="w"> </span><span class="n">fineSync</span><span class="p">(</span><span class="w"> </span><span class="n">nThreads</span><span class="w"> </span><span class="p">);</span> <span class="w"> </span><span class="c1">// as much chars as would fit into a cacheline</span> <span class="w"> </span><span class="k">struct</span><span class="w"> </span><span class="nc">alignas</span><span class="p">(</span><span class="n">CL_SIZE</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="kt">char</span><span class="w"> </span><span class="n">shareds</span><span class="p">[</span><span class="n">CL_SIZE</span><span class="p">];</span><span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="n">cacheLine</span><span class="p">;</span> <span class="w"> </span><span class="c1">// sum of all threads execution times</span> <span class="w"> </span><span class="n">atomic_int64_t</span><span class="w"> </span><span class="n">nsSum</span><span class="p">(</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">);</span> <span class="w"> </span><span class="k">for</span><span class="p">(</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">nThreads</span><span class="p">;</span><span class="w"> </span><span class="o">++</span><span class="n">t</span><span class="w"> </span><span class="p">)</span> <span class="w"> </span><span class="n">threads</span><span class="p">.</span><span class="n">emplace_back</span><span class="p">(</span> <span class="w"> </span><span class="p">[</span><span class="o">&</span><span class="p">](</span><span class="w"> </span><span class="kt">char</span><span class="w"> </span><span class="k">volatile</span><span class="w"> </span><span class="o">&</span><span class="n">c</span><span class="w"> </span><span class="p">)</span> <span class="w"> </span><span class="p">{</span> <span class="w"> </span><span class="n">coarseSync</span><span class="p">.</span><span class="n">arrive_and_wait</span><span class="p">();</span><span class="w"> </span><span class="c1">// synch beginning of thread execution on kernel-level</span> <span class="w"> </span><span class="k">if</span><span class="p">(</span><span class="w"> </span><span class="n">fineSync</span><span class="p">.</span><span class="n">fetch_sub</span><span class="p">(</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">memory_order</span><span class="o">::</span><span class="n">relaxed</span><span class="w"> </span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">)</span><span class="w"> </span><span class="c1">// fine-synch on user-level</span> <span class="w"> </span><span class="k">while</span><span class="p">(</span><span class="w"> </span><span class="n">fineSync</span><span class="p">.</span><span class="n">load</span><span class="p">(</span><span class="w"> </span><span class="n">memory_order</span><span class="o">::</span><span class="n">relaxed</span><span class="w"> </span><span class="p">)</span><span class="w"> </span><span class="p">);</span> <span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">start</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">high_resolution_clock</span><span class="o">::</span><span class="n">now</span><span class="p">();</span> <span class="w"> </span><span class="k">for</span><span class="p">(</span><span class="w"> </span><span class="kt">size_t</span><span class="w"> </span><span class="n">r</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">10'000'000</span><span class="p">;</span><span class="w"> </span><span class="n">r</span><span class="o">--</span><span class="p">;</span><span class="w"> </span><span class="p">)</span> <span class="w"> </span><span class="n">c</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">c</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span> <span class="w"> </span><span class="n">nsSum</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">duration_cast</span><span class="o"><</span><span class="n">nanoseconds</span><span class="o">></span><span class="p">(</span><span class="w"> </span><span class="n">high_resolution_clock</span><span class="o">::</span><span class="n">now</span><span class="p">()</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">start</span><span class="w"> </span><span class="p">).</span><span class="n">count</span><span class="p">();</span> <span class="w"> </span><span class="p">},</span><span class="w"> </span><span class="n">ref</span><span class="p">(</span><span class="w"> </span><span class="n">cacheLine</span><span class="p">.</span><span class="n">shareds</span><span class="p">[</span><span class="n">t</span><span class="p">]</span><span class="w"> </span><span class="p">)</span><span class="w"> </span><span class="p">);</span> <span class="w"> </span><span class="n">threads</span><span class="p">.</span><span class="n">resize</span><span class="p">(</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">);</span><span class="w"> </span><span class="c1">// join all threads</span> <span class="w"> </span><span class="n">cout</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n">nThreads</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">": "</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)(</span><span class="n">nsSum</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="p">(</span><span class="mf">1.0e7</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">nThreads</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mf">0.5</span><span class="p">)</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n">endl</span><span class="p">;</span> <span class="w"> </span><span class="p">}</span> <span class="p">}</span> </pre></div> <p>This code shows the effect of false sharing. It creates an increasing number of threads from one thread to the number of physical threads in the system. Each thread sequentially increments one byte of a cache line, which as a whole is shared among all threads. The higher the level of contention between threads, the longer each increment takes. This are the results on a Zen4 system with 16 cores and 32 threads: </p> <pre>1: 1 2: 4 3: 6 4: 9 5: 11 6: 13 7: 15 8: 17 9: 16 10: 18 11: 21 12: 25 13: 29 14: 35 15: 39 16: 41 17: 43 18: 44 19: 48 20: 49 21: 51 22: 53 23: 58 24: 61 25: 68 26: 75 27: 79 28: 82 29: 85 30: 88 31: 91 32: 94</pre> <p>As you can see, on the system in question it can take up to a 100 nanoseconds to complete an increment operation on the shared cache line, which corresponds to approx. 420 clock cycles on this CPU. </p> <div class="mw-heading mw-heading2"><h2 id="Mitigation">Mitigation</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=False_sharing&action=edit&section=3" title="Edit section: Mitigation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>There are ways of mitigating the effects of false sharing. For instance, false sharing in CPU caches can be prevented by reordering variables or adding <a href="/wiki/Data_structure_alignment#Data_structure_padding" title="Data structure alignment">padding</a> (unused bytes) between variables. However, some of these program changes may increase the size of the objects, leading to higher memory use.<sup id="cite_ref-Bolosky_2-1" class="reference"><a href="#cite_note-Bolosky-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> Compile-time data transformations can also mitigate false-sharing.<sup id="cite_ref-Jeremiassen_Eggers_1995_pp._179–188_3-0" class="reference"><a href="#cite_note-Jeremiassen_Eggers_1995_pp._179–188-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> However, some of these transformations may not always be allowed. For instance, the C++ programming language standard draft of C++23 mandates that data members must be laid out so that later members have higher addresses.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p><p>There are tools for detecting false sharing.<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> There are also systems that both detect and repair false sharing in executing programs. However, these systems incur some execution overhead.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=False_sharing&action=edit&section=4" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-Patterson_2012_p._537-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-Patterson_2012_p._537_1-0">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite id="CITEREFPatterson2012" class="citation book cs1">Patterson, David (2012). <i>Computer organization and design: the hardware/software interface</i>. 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New York, New York, USA: ACM Press. pp. <span class="nowrap">141–</span>154. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1145%2F2465351.2465366">10.1145/2465351.2465366</a>. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9781450319942" title="Special:BookSources/9781450319942"><bdi>9781450319942</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=conference&rft.atitle=Whose+cache+line+is+it+anyway%3F&rft.btitle=Proceedings+of+the+8th+ACM+European+Conference+on+Computer+Systems&rft.place=New+York%2C+New+York%2C+USA&rft.pages=%3Cspan+class%3D%22nowrap%22%3E141-%3C%2Fspan%3E154&rft.pub=ACM+Press&rft.date=2013&rft_id=info%3Adoi%2F10.1145%2F2465351.2465366&rft.isbn=9781450319942&rft.aulast=Nanavati&rft.aufirst=Mihir&rft.au=Spear%2C+Mark&rft.au=Taylor%2C+Nathan&rft.au=Rajagopalan%2C+Shriram&rft.au=Meyer%2C+Dutch+T.&rft.au=Aiello%2C+William&rft.au=Warfield%2C+Andrew&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFalse+sharing" class="Z3988"></span></span> </li> <li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLiuBerger2011" class="citation journal cs1">Liu, Tongping; Berger, Emery D. (2011-10-18). "SHERIFF: precise detection and automatic mitigation of false sharing". <i>ACM SIGPLAN Notices</i>. <b>46</b> (10). Association for Computing Machinery (ACM): <span class="nowrap">3–</span>18. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1145%2F2076021.2048070">10.1145/2076021.2048070</a>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/0362-1340">0362-1340</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=ACM+SIGPLAN+Notices&rft.atitle=SHERIFF%3A+precise+detection+and+automatic+mitigation+of+false+sharing&rft.volume=46&rft.issue=10&rft.pages=%3Cspan+class%3D%22nowrap%22%3E3-%3C%2Fspan%3E18&rft.date=2011-10-18&rft_id=info%3Adoi%2F10.1145%2F2076021.2048070&rft.issn=0362-1340&rft.aulast=Liu&rft.aufirst=Tongping&rft.au=Berger%2C+Emery+D.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFalse+sharing" class="Z3988"></span></span> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=False_sharing&action=edit&section=5" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a rel="nofollow" class="external text" href="https://parallelcomputing2017.wordpress.com/2017/03/17/understanding-false-sharing/">Easy Understanding on False Sharing</a></li> <li><a rel="nofollow" class="external text" href="http://cpp-today.blogspot.com/2008/05/false-sharing-hits-again.html">C++ today blog, False Sharing hits again!</a></li> <li><a rel="nofollow" class="external text" href="http://www.drdobbs.com/parallel/eliminate-false-sharing/217500206">Dr Dobbs article: Eliminate False Sharing</a></li> <li><a rel="nofollow" class="external text" href="http://psy-lob-saw.blogspot.sg/2013/05/know-thy-java-object-memory-layout.html">Be careful when trying to eliminate false sharing in Java</a></li></ul>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?useformat=desktop&type=1x1&usesul3=0" alt="" width="1" height="1" style="border: none; position: absolute;"></noscript> <div class="printfooter" data-nosnippet="">Retrieved from "<a dir="ltr" href="https://en.wikipedia.org/w/index.php?title=False_sharing&oldid=1189855845">https://en.wikipedia.org/w/index.php?title=False_sharing&oldid=1189855845</a>"</div></div> <div id="catlinks" class="catlinks" data-mw="interface"><div id="mw-normal-catlinks" class="mw-normal-catlinks"><a href="/wiki/Help:Category" title="Help:Category">Categories</a>: <ul><li><a href="/wiki/Category:Cache_coherency" title="Category:Cache coherency">Cache coherency</a></li><li><a href="/wiki/Category:Computer_memory" title="Category:Computer memory">Computer memory</a></li></ul></div><div id="mw-hidden-catlinks" class="mw-hidden-catlinks mw-hidden-cats-hidden">Hidden categories: <ul><li><a href="/wiki/Category:Articles_with_short_description" title="Category:Articles with short description">Articles with short description</a></li><li><a href="/wiki/Category:Short_description_matches_Wikidata" title="Category:Short description matches Wikidata">Short description matches Wikidata</a></li></ul></div></div> </div> </main> </div> <div class="mw-footer-container"> <footer id="footer" class="mw-footer" > <ul id="footer-info"> <li id="footer-info-lastmod"> This page was last edited on 14 December 2023, at 13:06<span class="anonymous-show"> (UTC)</span>.</li> <li id="footer-info-copyright">Text is available under the <a href="/wiki/Wikipedia:Text_of_the_Creative_Commons_Attribution-ShareAlike_4.0_International_License" title="Wikipedia:Text of the Creative Commons Attribution-ShareAlike 4.0 International License">Creative Commons Attribution-ShareAlike 4.0 License</a>; additional terms may apply. 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