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    <title>MongoDB Jira</title>
    <link>https://jira.mongodb.org</link>
    <description>This file is an XML representation of an issue</description>
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        <build-number>970001</build-number>
        <build-date>13-04-2023</build-date>
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<item>
            <title>[SERVER-29462] Eliminate possibility of false sharing in partitioned lock</title>
                <link>https://jira.mongodb.org/browse/SERVER-29462</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;The vector of mutexes inside catalog/util/partitioned.h does not ensure that the locks are on different cache lines.&lt;/p&gt;

&lt;p&gt;Ideally, we would use C++17&apos;s std::hardware_destructive_interference_size and alignas to fix this, however, not all of our toolchains currently support the required extended alignment.&lt;/p&gt;

&lt;p&gt;Instead, as a simpler fix, we should just allocate the mutexes on the heap, which is very likely to ensure that they land on different cachelines.&lt;/p&gt;</description>
                <environment></environment>
        <key id="390721">SERVER-29462</key>
            <summary>Eliminate possibility of false sharing in partitioned lock</summary>
                <type id="4" iconUrl="https://jira.mongodb.org/secure/viewavatar?size=xsmall&amp;avatarId=14710&amp;avatarType=issuetype">Improvement</type>
                                            <priority id="3" iconUrl="https://jira.mongodb.org/images/icons/priorities/major.svg">Major - P3</priority>
                        <status id="6" iconUrl="https://jira.mongodb.org/images/icons/statuses/closed.png" description="The issue is considered finished, the resolution is correct. Issues which are closed can be reopened.">Closed</status>
                    <statusCategory id="3" key="done" colorName="success"/>
                                    <resolution id="13201">Fixed</resolution>
                                        <assignee username="andrew.morrow@mongodb.com">Andrew Morrow</assignee>
                                    <reporter username="andrew.morrow@mongodb.com">Andrew Morrow</reporter>
                        <labels>
                    </labels>
                <created>Tue, 6 Jun 2017 18:36:52 +0000</created>
                <updated>Mon, 30 Oct 2023 23:16:21 +0000</updated>
                            <resolved>Wed, 5 Jul 2017 21:52:25 +0000</resolved>
                                                    <fixVersion>3.5.10</fixVersion>
                                    <component>Concurrency</component>
                    <component>Performance</component>
                                        <votes>0</votes>
                                    <watches>5</watches>
                                                                                                                <comments>
                            <comment id="1614665" author="xgen-internal-githook" created="Wed, 5 Jul 2017 21:52:06 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{u&apos;username&apos;: u&apos;acmorrow&apos;, u&apos;name&apos;: u&apos;Andrew Morrow&apos;, u&apos;email&apos;: u&apos;acm@mongodb.com&apos;}
&lt;p&gt;Message: &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-29462&quot; title=&quot;Eliminate possibility of false sharing in partitioned lock&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-29462&quot;&gt;&lt;del&gt;SERVER-29462&lt;/del&gt;&lt;/a&gt; Align locks in mongo::Paritioned to avoid false sharing&lt;/p&gt;

&lt;p&gt;This reverts commit 5a933be9235b7d02bb5c790c7ff7eba3a867c43a.&lt;br/&gt;
Branch: master&lt;br/&gt;
&lt;a href=&quot;https://github.com/mongodb/mongo/commit/12568fbc406678ebd98a93d121175b1f765c4766&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/mongodb/mongo/commit/12568fbc406678ebd98a93d121175b1f765c4766&lt;/a&gt;&lt;/p&gt;</comment>
                            <comment id="1612721" author="xgen-internal-githook" created="Mon, 3 Jul 2017 14:44:45 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{u&apos;username&apos;: u&apos;benety&apos;, u&apos;name&apos;: u&apos;Benety Goh&apos;, u&apos;email&apos;: u&apos;benety@mongodb.com&apos;}
&lt;p&gt;Message: Revert &quot;&lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-29462&quot; title=&quot;Eliminate possibility of false sharing in partitioned lock&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-29462&quot;&gt;&lt;del&gt;SERVER-29462&lt;/del&gt;&lt;/a&gt; Align locks in mongo::Paritioned to avoid false sharing&quot;&lt;/p&gt;

&lt;p&gt;This reverts commit edc858ca3a32974c07f027e6860a52ac6e89039b.&lt;br/&gt;
Branch: master&lt;br/&gt;
&lt;a href=&quot;https://github.com/mongodb/mongo/commit/5a933be9235b7d02bb5c790c7ff7eba3a867c43a&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/mongodb/mongo/commit/5a933be9235b7d02bb5c790c7ff7eba3a867c43a&lt;/a&gt;&lt;/p&gt;</comment>
                            <comment id="1612171" author="xgen-internal-githook" created="Sat, 1 Jul 2017 19:07:07 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{u&apos;username&apos;: u&apos;acmorrow&apos;, u&apos;name&apos;: u&apos;Andrew Morrow&apos;, u&apos;email&apos;: u&apos;acm@mongodb.com&apos;}
&lt;p&gt;Message: &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-29462&quot; title=&quot;Eliminate possibility of false sharing in partitioned lock&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-29462&quot;&gt;&lt;del&gt;SERVER-29462&lt;/del&gt;&lt;/a&gt; Align locks in mongo::Paritioned to avoid false sharing&lt;br/&gt;
Branch: master&lt;br/&gt;
&lt;a href=&quot;https://github.com/mongodb/mongo/commit/edc858ca3a32974c07f027e6860a52ac6e89039b&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/mongodb/mongo/commit/edc858ca3a32974c07f027e6860a52ac6e89039b&lt;/a&gt;&lt;/p&gt;</comment>
                            <comment id="1601654" author="acm" created="Tue, 20 Jun 2017 13:14:48 +0000"  >&lt;p&gt;&lt;a href=&quot;https://jira.mongodb.org/secure/ViewProfile.jspa?name=kyle.suarez&quot; class=&quot;user-hover&quot; rel=&quot;kyle.suarez&quot;&gt;kyle.suarez&lt;/a&gt; - Yes, and I actually plumbed it through the partitioned lock too, so I&apos;ll grab this ticket for now.&lt;/p&gt;</comment>
                            <comment id="1600911" author="kyle.suarez" created="Mon, 19 Jun 2017 17:29:53 +0000"  >&lt;p&gt;Looks like &lt;a href=&quot;https://jira.mongodb.org/secure/ViewProfile.jspa?name=acm&quot; class=&quot;user-hover&quot; rel=&quot;acm&quot;&gt;acm&lt;/a&gt; is actively working on &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-29712&quot; title=&quot;Polyfill std::hardware_{con,de}structive_interference_size&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-29712&quot;&gt;&lt;del&gt;SERVER-29712&lt;/del&gt;&lt;/a&gt;, so we could do this ticket after that work is in, rather than just allocating the mutexes on the heap.&lt;/p&gt;</comment>
                    </comments>
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                                        <issuelink>
            <issuekey id="395639">SERVER-29712</issuekey>
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            <issuekey id="394970">SERVER-29704</issuekey>
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            <issuekey id="242114">SERVER-21754</issuekey>
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