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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>
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<item>
            <title>[SERVER-28642] The Same query&apos;s performance reduces by 40 folds for 10 concurrent users</title>
                <link>https://jira.mongodb.org/browse/SERVER-28642</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;I have a complex aggregate query, that spans through 4 collections (3 collections have few hundred documents, and 1 collection has 15k documents) all have relevant indexes, that are indeed being used for the actual query.&lt;/p&gt;

&lt;p&gt;The Aggregate query in question takes about 2-3 seconds for 1 user, but if 10 parallel threads with same query are sent at same time, it takes 80-100 seconds.&lt;/p&gt;

&lt;p&gt;Environment details : single instance mongoDB Server&lt;br/&gt;
Version : 3.2.9&lt;br/&gt;
OS - RHEL 7.3&lt;/p&gt;

&lt;p&gt;The actual area where the slowness is happening is at the Global Locks. &lt;br/&gt;
The aggregate query should have read locks, but it is causing &quot;Global Write locks&quot;, refer attached snapshot.&lt;br/&gt;
(LEFT SIDE:  1 user sends aggregate query, the write locks can&apos;t be explained, but are not hurting as much)&lt;br/&gt;
(RIGHT SIDE : 10 users send same aggregate query, the write locks are taking significant time , whereas instead on READ locks were expected)&lt;/p&gt;</description>
                <environment></environment>
        <key id="371353">SERVER-28642</key>
            <summary>The Same query&apos;s performance reduces by 40 folds for 10 concurrent users</summary>
                <type id="6" iconUrl="https://jira.mongodb.org/secure/viewavatar?size=xsmall&amp;avatarId=14720&amp;avatarType=issuetype">Question</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="mark.agarunov">Mark Agarunov</assignee>
                                    <reporter username="wadhwanig">Gulshan Wadhwani</reporter>
                        <labels>
                    </labels>
                <created>Wed, 5 Apr 2017 21:14:23 +0000</created>
                <updated>Wed, 21 Jun 2017 21:23:29 +0000</updated>
                            <resolved>Wed, 24 May 2017 08:30:31 +0000</resolved>
                                    <version>3.2.9</version>
                                                    <component>Concurrency</component>
                                        <votes>0</votes>
                                    <watches>10</watches>
                                                                                                                <comments>
                            <comment id="1578626" author="thomas.schubert" created="Wed, 24 May 2017 08:30:31 +0000"  >&lt;p&gt;Hi &lt;a href=&quot;https://jira.mongodb.org/secure/ViewProfile.jspa?name=wadhwanig&quot; class=&quot;user-hover&quot; rel=&quot;wadhwanig&quot;&gt;wadhwanig&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 mark this ticket as resolved. 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;
Thomas&lt;/p&gt;</comment>
                            <comment id="1542649" author="mark.agarunov" created="Thu, 6 Apr 2017 15:44:42 +0000"  >&lt;p&gt;Hello &lt;a href=&quot;https://jira.mongodb.org/secure/ViewProfile.jspa?name=wadhwanig&quot; class=&quot;user-hover&quot; rel=&quot;wadhwanig&quot;&gt;wadhwanig&lt;/a&gt;,&lt;/p&gt;

&lt;p&gt;In addition to the diagnostic data from my previous request, please provide the complete logs from mongod from an instance where you see this behavior.&lt;/p&gt;

&lt;p&gt;Thanks,&lt;br/&gt;
Mark&lt;/p&gt;</comment>
                            <comment id="1542130" author="mark.agarunov" created="Wed, 5 Apr 2017 23:42:38 +0000"  >&lt;p&gt;Hello &lt;a href=&quot;https://jira.mongodb.org/secure/ViewProfile.jspa?name=wadhwanig&quot; class=&quot;user-hover&quot; rel=&quot;wadhwanig&quot;&gt;wadhwanig&lt;/a&gt;,&lt;/p&gt;

&lt;p&gt;Thank you for the report. To get a better insight into this issue, please archive (tar or zip) the &lt;tt&gt;$dbpath/diagnostic.data&lt;/tt&gt; directory and attach it to this ticket.&lt;/p&gt;

&lt;p&gt;Thanks,&lt;br/&gt;
Mark&lt;/p&gt;</comment>
                            <comment id="1542028" author="wadhwanig" created="Wed, 5 Apr 2017 21:23:04 +0000"  >&lt;p&gt;Just a slight correction, with 10 user+ situation, it is spending too much time on waiting for a write lock on MetaData/timeAcquiringMicros, but I think we should expect only read locks.&lt;/p&gt;</comment>
                    </comments>
                    <attachments>
                            <attachment id="153343" name="1User_vs_10User_Scenrio_for_SameAggregateQuery.jpg" size="306521" author="wadhwanig" created="Wed, 5 Apr 2017 21:13:43 +0000"/>
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