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        <build-number>970001</build-number>
        <build-date>13-04-2023</build-date>
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<item>
            <title>[SERVER-82690] Investigate performance gains by playing with decoration memory layout</title>
                <link>https://jira.mongodb.org/browse/SERVER-82690</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;In &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-82033&quot; title=&quot;Adapt existing FTDC controller to shard and router services&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-82033&quot;&gt;&lt;del&gt;SERVER-82033&lt;/del&gt;&lt;/a&gt; we moved the FTDC controller off of the ServiceContext decorations. As a result, we detected a &amp;gt;5% improvement in 95th percentile latencies by accident in some workloads.&lt;/p&gt;

&lt;p&gt;Our main hypothesis is that the decoration change shifted the memory layout of other decorations on the ServiceContext. That is to say, it changed the cache line &quot;split point&quot; of the structs coming afterwards. As a result, we removed some false sharing scenarios for metrics and this led to a latency drop.&lt;/p&gt;

&lt;p&gt;This ticket is about investigating how much we could gain from playing with the memory layout of decorations. Ideally we should also determine how best to take advantage of this in our codebase.&lt;/p&gt;</description>
                <environment></environment>
        <key id="2488948">SERVER-82690</key>
            <summary>Investigate performance gains by playing with decoration memory layout</summary>
                <type id="3" iconUrl="https://jira.mongodb.org/secure/viewavatar?size=xsmall&amp;avatarId=14718&amp;avatarType=issuetype">Task</type>
                                            <priority id="3" iconUrl="https://jira.mongodb.org/images/icons/priorities/major.svg">Major - P3</priority>
                        <status id="10038" iconUrl="https://jira.mongodb.org/images/icons/subtask.gif" description="">Backlog</status>
                    <statusCategory id="2" key="new" colorName="default"/>
                                    <resolution id="-1">Unresolved</resolution>
                                        <assignee username="backlog-server-servicearch">Backlog - Service Architecture</assignee>
                                    <reporter username="jordi.olivares-provencio@mongodb.com">Jordi Olivares Provencio</reporter>
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                <created>Thu, 2 Nov 2023 13:24:57 +0000</created>
                <updated>Tue, 14 Nov 2023 21:23:59 +0000</updated>
                                                                                                <votes>0</votes>
                                    <watches>9</watches>
                                                                                                                <comments>
                            <comment id="5880290" author="JIRAUSER1273619" created="Tue, 14 Nov 2023 21:23:45 +0000"  >&lt;p&gt;Moving this ticket under PM-3384&#160;as it&apos;ll be addressed as part of the project.&lt;/p&gt;

&lt;p&gt;cc &lt;a href=&quot;https://jira.mongodb.org/secure/ViewProfile.jspa?name=jordi.olivares-provencio%40mongodb.com&quot; class=&quot;user-hover&quot; rel=&quot;jordi.olivares-provencio@mongodb.com&quot;&gt;jordi.olivares-provencio@mongodb.com&lt;/a&gt;&#160;&lt;/p&gt;</comment>
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