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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-18674] Very low throughput during portion of checkpoint under WiredTiger</title>
                <link>https://jira.mongodb.org/browse/SERVER-18674</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;ul&gt;
	&lt;li&gt;132 GB memory, 32 processors, slowish SSDs, 20 GB WT cache&lt;/li&gt;
	&lt;li&gt;YCSB 10 fields/doc, 20M docs, 50/50 workload (zipfian distribution), 20 threads&lt;/li&gt;
	&lt;li&gt;data set size is ~23 GB but cache usage can grow to ~2x that and storage size can grow to ~3x, believe due to random update workload&lt;/li&gt;
	&lt;li&gt;to avoid &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-18314&quot; title=&quot;Stall during fdatasync phase of checkpoints under WiredTiger and EXT4&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-18314&quot;&gt;&lt;del&gt;SERVER-18314&lt;/del&gt;&lt;/a&gt; used either of the following (with same results)
	&lt;ul&gt;
		&lt;li&gt;ext4 mounted with -o commit=10000000&lt;/li&gt;
		&lt;li&gt;xfs&lt;/li&gt;
	&lt;/ul&gt;
	&lt;/li&gt;
&lt;/ul&gt;


&lt;p&gt;&lt;b&gt;3.1.3-pre (f5450e9bc5cf63c3dc4d9cb416713b0f6970e6d4)&lt;/b&gt;&lt;/p&gt;

&lt;p&gt;&lt;span class=&quot;image-wrap&quot; style=&quot;&quot;&gt;&lt;img src=&quot;https://jira.mongodb.org/secure/attachment/75865/75865_try-47.png&quot; width=&quot;900&quot; style=&quot;border: 0px solid black&quot; /&gt;&lt;/span&gt;&lt;/p&gt;

&lt;p&gt;&lt;b&gt;3.1.3 (51ad8eff0d50387f0565d23a15e7ba1db0ea962c)&lt;/b&gt;&lt;/p&gt;

&lt;p&gt;&lt;span class=&quot;image-wrap&quot; style=&quot;&quot;&gt;&lt;img src=&quot;https://jira.mongodb.org/secure/attachment/75866/75866_try-49.png&quot; width=&quot;900&quot; style=&quot;border: 0px solid black&quot; /&gt;&lt;/span&gt;&lt;/p&gt;

&lt;p&gt;&lt;b&gt;3.1.4-pre (36ac7a5d8a6cc4f6280f90ce743ab05a77a541a8)&lt;/b&gt;&lt;/p&gt;

&lt;p&gt;&lt;span class=&quot;image-wrap&quot; style=&quot;&quot;&gt;&lt;img src=&quot;https://jira.mongodb.org/secure/attachment/75867/75867_try-50.png&quot; width=&quot;900&quot; style=&quot;border: 0px solid black&quot; /&gt;&lt;/span&gt;&lt;/p&gt;


&lt;p&gt;Notes:&lt;/p&gt;
&lt;ul&gt;
	&lt;li&gt;issue for this ticket is period from C-D; B-C appears to be different issue.&lt;/li&gt;
	&lt;li&gt;appears to be a regression in 3.1.3&lt;/li&gt;
	&lt;li&gt;same result with xfs and ext4 -o commit=largenumber&lt;/li&gt;
	&lt;li&gt;superficially similar to &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-18314&quot; title=&quot;Stall during fdatasync phase of checkpoints under WiredTiger and EXT4&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-18314&quot;&gt;&lt;del&gt;SERVER-18314&lt;/del&gt;&lt;/a&gt; in that it coincides with an fdatasync but:
	&lt;ul&gt;
		&lt;li&gt;used settings that were shown to eliminate &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-18314&quot; title=&quot;Stall during fdatasync phase of checkpoints under WiredTiger and EXT4&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-18314&quot;&gt;&lt;del&gt;SERVER-18314&lt;/del&gt;&lt;/a&gt; issue&lt;/li&gt;
		&lt;li&gt;writes did not seem to be blocked as in &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-18314&quot; title=&quot;Stall during fdatasync phase of checkpoints under WiredTiger and EXT4&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-18314&quot;&gt;&lt;del&gt;SERVER-18314&lt;/del&gt;&lt;/a&gt;&lt;/li&gt;
		&lt;li&gt;only affected one of the two periods where fadatasync runs&lt;/li&gt;
		&lt;li&gt;so appears to be WT issue, not platform issue&lt;/li&gt;
	&lt;/ul&gt;
	&lt;/li&gt;
	&lt;li&gt;attempted to get stack traces but it appears process is not interruptible during the fdatasync and this issue coincides with that&lt;/li&gt;
&lt;/ul&gt;
</description>
                <environment></environment>
        <key id="206745">SERVER-18674</key>
            <summary>Very low throughput during portion of checkpoint under WiredTiger</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="9">Done</resolution>
                                        <assignee username="david.hows">David Hows</assignee>
                                    <reporter username="bruce.lucas@mongodb.com">Bruce Lucas</reporter>
                        <labels>
                    </labels>
                <created>Wed, 27 May 2015 13:50:37 +0000</created>
                <updated>Thu, 14 Apr 2016 15:19:16 +0000</updated>
                            <resolved>Thu, 16 Jul 2015 03:02:31 +0000</resolved>
                                    <version>3.1.3</version>
                                                    <component>WiredTiger</component>
                                        <votes>0</votes>
                                    <watches>8</watches>
                                                                                                                <comments>
                            <comment id="967472" author="david.hows" created="Thu, 16 Jul 2015 03:01:21 +0000"  >&lt;p&gt;Marking this as Done based on my testing, as I was unable to reproduce.&lt;/p&gt;

&lt;p&gt;There have been a number of changes to related parts of MongoDB and WT including the linked &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-18875&quot; title=&quot;Oplog performance on WT degrades over time after accumulation of deleted items&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-18875&quot;&gt;&lt;del&gt;SERVER-18875&lt;/del&gt;&lt;/a&gt;, &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-18829&quot; title=&quot;Cache usage exceeds configured maximum during index builds under WiredTiger&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-18829&quot;&gt;&lt;del&gt;SERVER-18829&lt;/del&gt;&lt;/a&gt; and &lt;a href=&quot;https://jira.mongodb.org/browse/WT-1907&quot; title=&quot;Speed up transaction-refresh&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-1907&quot;&gt;&lt;del&gt;WT-1907&lt;/del&gt;&lt;/a&gt;. Suspect that some combination of those resolved the underlying issue.&lt;/p&gt;</comment>
                            <comment id="966361" author="david.hows" created="Wed, 15 Jul 2015 03:55:34 +0000"  >&lt;p&gt;I tested this along with &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-18677&quot; title=&quot;Throughput drop during transaction pinned phase of checkpoints under WiredTiger (larger data set)&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-18677&quot;&gt;&lt;del&gt;SERVER-18677&lt;/del&gt;&lt;/a&gt;.&lt;/p&gt;

&lt;p&gt;Ran this on an r3.4xlarge using Bruce&apos;s setup and MongoDB master as at 15/7/2015 Hash: 3f301ac62e&lt;/p&gt;

&lt;p&gt;The instance had a generic (slow) SSD storage formatted using XFS.&lt;/p&gt;

&lt;p&gt;With the 10M workload there was no drop in throughput associated with checkpoints as seen in Bruce&apos;s graphs. There was only one small drop in query throughput and this was associated with an increase in writes (update ops).&lt;/p&gt;

&lt;p&gt;With the 20M workload there were no sustained drops in throughput&lt;/p&gt;</comment>
                            <comment id="958090" author="michael.cahill" created="Mon, 6 Jul 2015 02:32:39 +0000"  >&lt;p&gt;&lt;a href=&quot;https://jira.mongodb.org/secure/ViewProfile.jspa?name=david.hows&quot; class=&quot;user-hover&quot; rel=&quot;david.hows&quot;&gt;david.hows&lt;/a&gt; can you please retest against MongoDB master?&lt;/p&gt;</comment>
                    </comments>
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                            <issuelinktype id="10012">
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                                            <outwardlinks description="related to">
                                        <issuelink>
            <issuekey id="209236">SERVER-18875</issuekey>
        </issuelink>
            <issuelink>
            <issuekey id="206780">SERVER-18677</issuekey>
        </issuelink>
            <issuelink>
            <issuekey id="208369">SERVER-18829</issuekey>
        </issuelink>
            <issuelink>
            <issuekey id="200653">WT-1907</issuekey>
        </issuelink>
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                                        <issuelink>
            <issuekey id="201913">SERVER-18314</issuekey>
        </issuelink>
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                            <attachment id="75867" name="try-50.png" size="191253" author="bruce.lucas@mongodb.com" created="Wed, 27 May 2015 13:50:37 +0000"/>
                            <attachment id="76369" name="wtmonitor.html" size="660853" author="sue.loverso@mongodb.com" created="Mon, 1 Jun 2015 19:29:41 +0000"/>
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