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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>
    <language>en-us</language>    <build-info>
        <version>9.7.1</version>
        <build-number>970001</build-number>
        <build-date>13-04-2023</build-date>
    </build-info>


<item>
            <title>[SERVER-57181] Evict server should be parallelized</title>
                <link>https://jira.mongodb.org/browse/SERVER-57181</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;Evict-server is single-threaded in wiredtiger. Sometimes it becomes the bottleneck under heavy write workloads. As WT cache-used and cache-dirty get too high, app threads are stuck in evict-worker process but won&apos;t help.&lt;/p&gt;

&lt;p&gt;Single-threaded evict-server may lead 2 problems:&lt;/p&gt;
&lt;ol&gt;
	&lt;li&gt;Reduce write performance even in multi-core machines.&lt;/li&gt;
	&lt;li&gt;The related cpu core usage spikes to 100% when evict-server is busy.&lt;/li&gt;
&lt;/ol&gt;
</description>
                <environment></environment>
        <key id="1718681">SERVER-57181</key>
            <summary>Evict server should be parallelized</summary>
                <type id="1" iconUrl="https://jira.mongodb.org/secure/viewavatar?size=xsmall&amp;avatarId=14703&amp;avatarType=issuetype">Bug</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="4">Incomplete</resolution>
                                        <assignee username="dmitry.agranat@mongodb.com">Dmitry Agranat</assignee>
                                    <reporter username="pengzhenyi">peng zhenyi</reporter>
                        <labels>
                    </labels>
                <created>Mon, 17 May 2021 12:47:00 +0000</created>
                <updated>Thu, 24 Jun 2021 12:04:11 +0000</updated>
                            <resolved>Thu, 24 Jun 2021 12:04:11 +0000</resolved>
                                                                                        <votes>0</votes>
                                    <watches>9</watches>
                                                                                                                <comments>
                            <comment id="3896223" author="dmitry.agranat" created="Thu, 24 Jun 2021 12:03:59 +0000"  >&lt;p&gt;Hi &lt;a href=&quot;https://jira.mongodb.org/secure/ViewProfile.jspa?name=pengzhenyi&quot; class=&quot;user-hover&quot; rel=&quot;pengzhenyi&quot;&gt;pengzhenyi&lt;/a&gt;,&lt;/p&gt;

&lt;p&gt;We haven&#8217;t heard back from you for some time, so I&#8217;m going to close this ticket. If this is still an issue for you, please provide additional information and we will reopen the ticket.&lt;/p&gt;

&lt;p&gt;Regards,&lt;br/&gt;
Dima&lt;/p&gt;</comment>
                            <comment id="3868394" author="dmitry.agranat" created="Wed, 9 Jun 2021 13:26:13 +0000"  >&lt;p&gt;Hi &lt;a href=&quot;https://jira.mongodb.org/secure/ViewProfile.jspa?name=pengzhenyi&quot; class=&quot;user-hover&quot; rel=&quot;pengzhenyi&quot;&gt;pengzhenyi&lt;/a&gt;,&lt;/p&gt;

&lt;p&gt;We still need additional information to diagnose the problem. If this is still an issue for you, would you please upload the requested information?&lt;/p&gt;

&lt;p&gt;Thanks,&lt;br/&gt;
Dima&lt;/p&gt;</comment>
                            <comment id="3836279" author="dmitry.agranat" created="Tue, 25 May 2021 11:50:50 +0000"  >&lt;p&gt;Hi &lt;a href=&quot;https://jira.mongodb.org/secure/ViewProfile.jspa?name=pengzhenyi&quot; class=&quot;user-hover&quot; rel=&quot;pengzhenyi&quot;&gt;pengzhenyi&lt;/a&gt;, to understand the reported issue, we&apos;d like to review the workload you are executing.&lt;/p&gt;

&lt;p&gt;Would you please archive (tar or zip) the mongod.log files covering the incident and the &lt;tt&gt;$dbpath/diagnostic.data&lt;/tt&gt; directory (the contents are described &lt;a href=&quot;https://docs.mongodb.com/manual/administration/analyzing-mongodb-performance/#full-time-diagnostic-data-capture&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;here&lt;/a&gt;) and upload them to this &lt;a href=&quot;https://10gen-httpsupload.s3.amazonaws.com/upload_forms/f0ebe00b-bb64-4ef7-8ced-ca9453306b27.html&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;support uploader&lt;/a&gt; location?&lt;/p&gt;

&lt;p&gt;Files uploaded to this portal are visible only to MongoDB employees and are routinely deleted after some time.&lt;/p&gt;

&lt;p&gt;Please mention the exact timestamp and timezone for the start/stop of the event in question.&lt;/p&gt;

&lt;p&gt;Thanks,&lt;br/&gt;
Dima&lt;/p&gt;
</comment>
                            <comment id="3802630" author="pengzhenyi" created="Fri, 21 May 2021 09:40:12 +0000"  >&lt;p&gt;HI, &lt;a href=&quot;https://jira.mongodb.org/secure/ViewProfile.jspa?name=brian.lane&quot; class=&quot;user-hover&quot; rel=&quot;brian.lane&quot;&gt;brian.lane&lt;/a&gt;&lt;/p&gt;

&lt;p&gt;&#160;&lt;/p&gt;

&lt;p&gt;I found this issue in&#160; v3.2 (r3.2.10) and v4.0 (r4.0.3)&#160; which under heavy-update workloads.&#160;&lt;/p&gt;

&lt;p&gt;I ran &apos;pstack&apos; of the thread which consumed the entire single cpu core, and conformed that it was the evict-server task.&lt;/p&gt;

&lt;p&gt;I also read the latest WT release code (WT 10.0.0), and found that only one thread can be evict-server which gets the &apos;evict_pass_lock&apos;.&lt;/p&gt;

&lt;p&gt;&#160;&lt;/p&gt;

&lt;p&gt;Here are my questions&lt;/p&gt;
&lt;ol&gt;
	&lt;li&gt;Evict-server is single-threaded, Is there any reason about this?&lt;/li&gt;
	&lt;li&gt;Evict-server may cause cpu usage spikes, and even become the bottleneck of WT. Is there any way to solve this? I tried to increase more evict threads, but did not help.&lt;/li&gt;
	&lt;li&gt;Does WT community have any plans to make evict-server multi-threaded?&lt;/li&gt;
&lt;/ol&gt;
</comment>
                            <comment id="3780085" author="brian.lane" created="Tue, 18 May 2021 05:35:59 +0000"  >&lt;p&gt;HI &lt;a href=&quot;https://jira.mongodb.org/secure/ViewProfile.jspa?name=pengzhenyi&quot; class=&quot;user-hover&quot; rel=&quot;pengzhenyi&quot;&gt;pengzhenyi&lt;/a&gt;,&lt;/p&gt;

&lt;p&gt;Thanks for reaching out with this issue.  &lt;/p&gt;

&lt;p&gt;Could you give us more details about your workload and how often you are experiencing this behavior?&lt;/p&gt;

</comment>
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                            <attachment id="316195" name="image-2021-05-21-17-28-30-711.png" size="60023" author="pengzhenyi" created="Fri, 21 May 2021 09:28:33 +0000"/>
                            <attachment id="316196" name="image-2021-05-21-17-30-18-131.png" size="90520" author="pengzhenyi" created="Fri, 21 May 2021 09:30:19 +0000"/>
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