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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-26753] Minor speed regression (13%) and &apos;choppy&apos; performance in 3.4 vs 3.2</title>
                <link>https://jira.mongodb.org/browse/SERVER-26753</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;OS is Win2012R2.&lt;/p&gt;

&lt;p&gt;When comparing my workload on the 3.4rc1 vs 3.2.10 there is a minor speed regression (13%) which appears to be mainly due to some intermittent activity (eviction?).&lt;/p&gt;

&lt;p&gt;I see the cpu spike to 100% every ~10-20 seconds with a corresponding speed drop. In 3.2, the cpu stays relatively flat.&lt;/p&gt;

&lt;p&gt;This is minor but thought you might like to know.&lt;/p&gt;
</description>
                <environment></environment>
        <key id="326442">SERVER-26753</key>
            <summary>Minor speed regression (13%) and &apos;choppy&apos; performance in 3.4 vs 3.2</summary>
                <type id="3" iconUrl="https://jira.mongodb.org/secure/viewavatar?size=xsmall&amp;avatarId=14718&amp;avatarType=issuetype">Task</type>
                                            <priority id="4" iconUrl="https://jira.mongodb.org/images/icons/priorities/minor.svg">Minor - P4</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="michael.cahill@mongodb.com">Michael Cahill</assignee>
                                    <reporter username="nick@innsenroute.com">Nick Judson</reporter>
                        <labels>
                            <label>code-only</label>
                    </labels>
                <created>Mon, 24 Oct 2016 19:31:59 +0000</created>
                <updated>Wed, 23 Nov 2016 18:54:00 +0000</updated>
                            <resolved>Mon, 7 Nov 2016 06:01:16 +0000</resolved>
                                    <version>3.4.0-rc1</version>
                                    <fixVersion>3.2.11</fixVersion>
                    <fixVersion>3.4.0-rc3</fixVersion>
                                    <component>WiredTiger</component>
                                        <votes>0</votes>
                                    <watches>11</watches>
                                                                                                                <comments>
                            <comment id="1428588" author="xgen-internal-githook" created="Mon, 7 Nov 2016 22:03:09 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{u&apos;name&apos;: u&apos;Ramon Fernandez&apos;, u&apos;email&apos;: u&apos;ramon@mongodb.com&apos;}
&lt;p&gt;Message: Import wiredtiger: 2e2d5fe23badac038944bdc6639eb62d77136f1a from branch mongodb-3.2&lt;/p&gt;

&lt;p&gt;ref: b11ed312ce..2e2d5fe23b&lt;br/&gt;
for: 3.2.11&lt;/p&gt;

&lt;p&gt;&lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-26753&quot; title=&quot;Minor speed regression (13%) and &amp;#39;choppy&amp;#39; performance in 3.4 vs 3.2&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-26753&quot;&gt;&lt;del&gt;SERVER-26753&lt;/del&gt;&lt;/a&gt;  Minor speed regression (13%) and &apos;choppy&apos; performance in 3.4 vs 3.2&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-2415&quot; title=&quot;Add option for join cursors to return false positives from a Bloom filter&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-2415&quot;&gt;&lt;del&gt;WT-2415&lt;/del&gt;&lt;/a&gt;       Add option for join cursors to return false positives from a Bloom filter&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-2945&quot; title=&quot;Occasional hang running reconfigure fuzz test&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-2945&quot;&gt;&lt;del&gt;WT-2945&lt;/del&gt;&lt;/a&gt;       Occasional hang running reconfigure fuzz test&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-2947&quot; title=&quot;test suite populate functions need refactoring&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-2947&quot;&gt;&lt;del&gt;WT-2947&lt;/del&gt;&lt;/a&gt;       test suite populate functions need refactoring&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-2953&quot; title=&quot;Test format failure - stuck cache with 1/42MB dirty&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-2953&quot;&gt;&lt;del&gt;WT-2953&lt;/del&gt;&lt;/a&gt;       Test format failure - stuck cache with 1/42MB dirty&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-2961&quot; title=&quot;Add a version drop-down to the web version of the docs&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-2961&quot;&gt;&lt;del&gt;WT-2961&lt;/del&gt;&lt;/a&gt;       Add a version drop-down to the web version of the docs&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-2964&quot; title=&quot;WTPERF parallel-pop-btree hung in populate phase&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-2964&quot;&gt;&lt;del&gt;WT-2964&lt;/del&gt;&lt;/a&gt;       WTPERF parallel-pop-btree hung in populate phase&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-2968&quot; title=&quot;backup cursor opens every file&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-2968&quot;&gt;&lt;del&gt;WT-2968&lt;/del&gt;&lt;/a&gt;       backup cursor opens every file&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-2971&quot; title=&quot;Add documentation for raw-compression to the tune_compression page in WT docs&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-2971&quot;&gt;&lt;del&gt;WT-2971&lt;/del&gt;&lt;/a&gt;       Add documentation for raw-compression to the tune_compression page in WT docs&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-2975&quot; title=&quot;Reduce the memory allocated for statistics&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-2975&quot;&gt;&lt;del&gt;WT-2975&lt;/del&gt;&lt;/a&gt;       Reduce the memory allocated for statistics&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-2991&quot; title=&quot;Coverity issue 1365198&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-2991&quot;&gt;&lt;del&gt;WT-2991&lt;/del&gt;&lt;/a&gt;       Coverity issue 1365198&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-2998&quot; title=&quot;Add error messages to error returns that might be confusing.&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-2998&quot;&gt;&lt;del&gt;WT-2998&lt;/del&gt;&lt;/a&gt;       Add error messages to error returns that might be confusing.&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-2999&quot; title=&quot;Memory leak in join WT_CURSOR with custom extractor&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-2999&quot;&gt;&lt;del&gt;WT-2999&lt;/del&gt;&lt;/a&gt;       Memory leak in join WT_CURSOR with custom extractor&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-3001&quot; title=&quot;WT_EXTENSION_API references are named inconsistently.&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-3001&quot;&gt;&lt;del&gt;WT-3001&lt;/del&gt;&lt;/a&gt;       WT_EXTENSION_API references are named inconsistently.&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-3003&quot; title=&quot;log generation should not auto generate the record and op types&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-3003&quot;&gt;&lt;del&gt;WT-3003&lt;/del&gt;&lt;/a&gt;       log generation should not auto generate the record and op types&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-3005&quot; title=&quot;Add top-level .gitignore file.&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-3005&quot;&gt;&lt;del&gt;WT-3005&lt;/del&gt;&lt;/a&gt;       Add top-level .gitignore file.&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-3007&quot; title=&quot;Remove duplicated word in comment&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-3007&quot;&gt;&lt;del&gt;WT-3007&lt;/del&gt;&lt;/a&gt;       Remove duplicated word in comment&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-3008&quot; title=&quot;Run wtperf stress testing against all maintained branches&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-3008&quot;&gt;&lt;del&gt;WT-3008&lt;/del&gt;&lt;/a&gt;       Run wtperf stress testing against all maintained branches&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-3009&quot; title=&quot;Test format hung/aborted with small cache (sub 10mB)&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-3009&quot;&gt;&lt;del&gt;WT-3009&lt;/del&gt;&lt;/a&gt;       Test format hung/aborted with small cache (sub 10mB)&lt;br/&gt;
Branch: v3.2&lt;br/&gt;
&lt;a href=&quot;https://github.com/mongodb/mongo/commit/7c626977cf052314d09648d1061e07c44e964264&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/mongodb/mongo/commit/7c626977cf052314d09648d1061e07c44e964264&lt;/a&gt;&lt;/p&gt;</comment>
                            <comment id="1427575" author="michael.cahill" created="Mon, 7 Nov 2016 06:00:59 +0000"  >&lt;p&gt;&lt;a href=&quot;https://jira.mongodb.org/secure/ViewProfile.jspa?name=nick%40innsenroute.com&quot; class=&quot;user-hover&quot; rel=&quot;nick@innsenroute.com&quot;&gt;nick@innsenroute.com&lt;/a&gt;, thanks for the update: this is a little puzzling.&lt;/p&gt;

&lt;p&gt;We can see clearly in the stats that the read lock spinning has been resolved: in 3.2.9 your data shows occasional spikes in this statistic of 150M/s, in 3.2.10 there were many more spikes going up to 450M/s.  With the patch applied, this stat never goes above 166K/s (i.e., 1000x lower).&lt;/p&gt;

&lt;p&gt;I&apos;m not sure what to make of the lower performance: we don&apos;t track system statistics such as CPU and disk in MongoDB 3.2, so I can&apos;t correlate performance with CPU use from this data.&lt;/p&gt;

&lt;p&gt;I am going to close this ticket because I believe the underlying issue has been resolved by changes that will be in the next release of MongoDB.  If you want more followup, please reopen or file a new ticket.&lt;/p&gt;</comment>
                            <comment id="1427551" author="xgen-internal-githook" created="Mon, 7 Nov 2016 05:48:51 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{u&apos;username&apos;: u&apos;michaelcahill&apos;, u&apos;name&apos;: u&apos;Michael Cahill&apos;, u&apos;email&apos;: u&apos;michael.cahill@mongodb.com&apos;}
&lt;p&gt;Message: Import wiredtiger: 74430da40c96247c0a0d92f011ccfb2b175f1f32 from branch mongodb-3.4&lt;/p&gt;

&lt;p&gt;ref: ef9a7983ea..74430da40c&lt;br/&gt;
for: 3.4.0&lt;/p&gt;

&lt;p&gt;&lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-26753&quot; title=&quot;Minor speed regression (13%) and &amp;#39;choppy&amp;#39; performance in 3.4 vs 3.2&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-26753&quot;&gt;&lt;del&gt;SERVER-26753&lt;/del&gt;&lt;/a&gt;  Minor speed regression (13%) and &apos;choppy&apos; performance in 3.4 vs 3.2&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-2415&quot; title=&quot;Add option for join cursors to return false positives from a Bloom filter&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-2415&quot;&gt;&lt;del&gt;WT-2415&lt;/del&gt;&lt;/a&gt;       Add option for join cursors to return false positives&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-2945&quot; title=&quot;Occasional hang running reconfigure fuzz test&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-2945&quot;&gt;&lt;del&gt;WT-2945&lt;/del&gt;&lt;/a&gt;       Occasional hang running reconfigure fuzz test&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-2947&quot; title=&quot;test suite populate functions need refactoring&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-2947&quot;&gt;&lt;del&gt;WT-2947&lt;/del&gt;&lt;/a&gt;       test suite populate functions need refactoring&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-2953&quot; title=&quot;Test format failure - stuck cache with 1/42MB dirty&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-2953&quot;&gt;&lt;del&gt;WT-2953&lt;/del&gt;&lt;/a&gt;       Test format failure - stuck cache with 1/42MB dirty&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-2961&quot; title=&quot;Add a version drop-down to the web version of the docs&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-2961&quot;&gt;&lt;del&gt;WT-2961&lt;/del&gt;&lt;/a&gt;       Add a version drop-down to the web version of the docs&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-2964&quot; title=&quot;WTPERF parallel-pop-btree hung in populate phase&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-2964&quot;&gt;&lt;del&gt;WT-2964&lt;/del&gt;&lt;/a&gt;       WTPERF parallel-pop-btree hung in populate phase&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-2968&quot; title=&quot;backup cursor opens every file&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-2968&quot;&gt;&lt;del&gt;WT-2968&lt;/del&gt;&lt;/a&gt;       backup cursor opens every file&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-2971&quot; title=&quot;Add documentation for raw-compression to the tune_compression page in WT docs&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-2971&quot;&gt;&lt;del&gt;WT-2971&lt;/del&gt;&lt;/a&gt;       Add documentation for raw compression to the WT docs&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-2975&quot; title=&quot;Reduce the memory allocated for statistics&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-2975&quot;&gt;&lt;del&gt;WT-2975&lt;/del&gt;&lt;/a&gt;       Reduce the memory allocated for statistics&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-2991&quot; title=&quot;Coverity issue 1365198&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-2991&quot;&gt;&lt;del&gt;WT-2991&lt;/del&gt;&lt;/a&gt;       Coverity issue 1365198&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-2998&quot; title=&quot;Add error messages to error returns that might be confusing.&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-2998&quot;&gt;&lt;del&gt;WT-2998&lt;/del&gt;&lt;/a&gt;       Add error messages to error returns that might be confusing.&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-2999&quot; title=&quot;Memory leak in join WT_CURSOR with custom extractor&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-2999&quot;&gt;&lt;del&gt;WT-2999&lt;/del&gt;&lt;/a&gt;       Memory leak in join WT_CURSOR with custom extractor&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-3001&quot; title=&quot;WT_EXTENSION_API references are named inconsistently.&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-3001&quot;&gt;&lt;del&gt;WT-3001&lt;/del&gt;&lt;/a&gt;       WT_EXTENSION_API references are named inconsistently.&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-3003&quot; title=&quot;log generation should not auto generate the record and op types&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-3003&quot;&gt;&lt;del&gt;WT-3003&lt;/del&gt;&lt;/a&gt;       log generation should not auto generate the record and op types&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-3005&quot; title=&quot;Add top-level .gitignore file.&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-3005&quot;&gt;&lt;del&gt;WT-3005&lt;/del&gt;&lt;/a&gt;       Add top-level .gitignore file.&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-3007&quot; title=&quot;Remove duplicated word in comment&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-3007&quot;&gt;&lt;del&gt;WT-3007&lt;/del&gt;&lt;/a&gt;       Remove duplicated word in comment&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-3008&quot; title=&quot;Run wtperf stress testing against all maintained branches&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-3008&quot;&gt;&lt;del&gt;WT-3008&lt;/del&gt;&lt;/a&gt;       Run wtperf stress testing against all maintained branches&lt;br/&gt;
&lt;a href=&quot;https://jira.mongodb.org/browse/WT-3009&quot; title=&quot;Test format hung/aborted with small cache (sub 10mB)&quot; class=&quot;issue-link&quot; data-issue-key=&quot;WT-3009&quot;&gt;&lt;del&gt;WT-3009&lt;/del&gt;&lt;/a&gt;       Test format hung/aborted with small cache (sub 10mB)&lt;br/&gt;
Branch: master&lt;br/&gt;
&lt;a href=&quot;https://github.com/mongodb/mongo/commit/0f0db45770f45eab89bd7c2530a259f5ed5b6334&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/mongodb/mongo/commit/0f0db45770f45eab89bd7c2530a259f5ed5b6334&lt;/a&gt;&lt;/p&gt;</comment>
                            <comment id="1426481" author="nick@innsenroute.com" created="Fri, 4 Nov 2016 17:39:23 +0000"  >&lt;p&gt;...and after rebooting the MongoDb host, it appears to have reverted back to the behavior I&apos;m used to...&lt;/p&gt;</comment>
                            <comment id="1426430" author="nick@innsenroute.com" created="Fri, 4 Nov 2016 16:53:06 +0000"  >&lt;p&gt;Must be something to do with my environment since I see a similar behavior in 3.2.9. Interesting to note that 3.2.9 still shows a better performance / lower cpu usage. I&apos;m attaching the 3.2.9 run.&lt;/p&gt;</comment>
                            <comment id="1426424" author="nick@innsenroute.com" created="Fri, 4 Nov 2016 16:45:01 +0000"  >&lt;p&gt;Run from scratch using custom build.&lt;/p&gt;</comment>
                            <comment id="1426416" author="nick@innsenroute.com" created="Fri, 4 Nov 2016 16:42:59 +0000"  >&lt;p&gt;~Michael Cahill - I came in this morning to run another test and re-tried this test again (wiped everything clean this time). I don&apos;t know what has changed but I&apos;m seeing a different behavior now with long blocks of 100% cpu usage. I&apos;m going to attach some more diagnostic files for you to look at. So...this may not be completely resolved yet.&lt;/p&gt;</comment>
                            <comment id="1426072" author="xgen-internal-githook" created="Fri, 4 Nov 2016 10:06:25 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{u&apos;username&apos;: u&apos;michaelcahill&apos;, u&apos;name&apos;: u&apos;Michael Cahill&apos;, u&apos;email&apos;: u&apos;michael.cahill@mongodb.com&apos;}
&lt;p&gt;Message: &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-26753&quot; title=&quot;Minor speed regression (13%) and &amp;#39;choppy&amp;#39; performance in 3.4 vs 3.2&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-26753&quot;&gt;&lt;del&gt;SERVER-26753&lt;/del&gt;&lt;/a&gt; Add a call to spin on rwlocks with no active writers  (#3126)&lt;br/&gt;
Branch: mongodb-3.2&lt;br/&gt;
&lt;a href=&quot;https://github.com/wiredtiger/wiredtiger/commit/f418cea41b61f47fda740751495f9f5d39d814fd&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/wiredtiger/wiredtiger/commit/f418cea41b61f47fda740751495f9f5d39d814fd&lt;/a&gt;&lt;/p&gt;</comment>
                            <comment id="1426061" author="xgen-internal-githook" created="Fri, 4 Nov 2016 10:06:12 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{u&apos;username&apos;: u&apos;michaelcahill&apos;, u&apos;name&apos;: u&apos;Michael Cahill&apos;, u&apos;email&apos;: u&apos;michael.cahill@mongodb.com&apos;}
&lt;p&gt;Message: &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-26753&quot; title=&quot;Minor speed regression (13%) and &amp;#39;choppy&amp;#39; performance in 3.4 vs 3.2&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-26753&quot;&gt;&lt;del&gt;SERVER-26753&lt;/del&gt;&lt;/a&gt; Don&apos;t spin on a read-lock in a tight loop. (#3113)&lt;/p&gt;

&lt;ul&gt;
	&lt;li&gt;&lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-26753&quot; title=&quot;Minor speed regression (13%) and &amp;#39;choppy&amp;#39; performance in 3.4 vs 3.2&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-26753&quot;&gt;&lt;del&gt;SERVER-26753&lt;/del&gt;&lt;/a&gt; Don&apos;t spin on a read-lock in a tight loop.&lt;/li&gt;
&lt;/ul&gt;


&lt;p&gt;We could be starving a thread that we are waiting on of CPU.&lt;/p&gt;

&lt;ul&gt;
	&lt;li&gt;Switch to yielding on rwlocks rather than sleeping.&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;Revert the attempt to be clever when spinning on rwlocks.&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;Spin getting a read lock while it is available to readers.&lt;br/&gt;
Branch: mongodb-3.2&lt;br/&gt;
&lt;a href=&quot;https://github.com/wiredtiger/wiredtiger/commit/b90338afdc09c50cf3a321a9778c8e650fc3d6a1&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/wiredtiger/wiredtiger/commit/b90338afdc09c50cf3a321a9778c8e650fc3d6a1&lt;/a&gt;&lt;/li&gt;
&lt;/ul&gt;
</comment>
                            <comment id="1426060" author="xgen-internal-githook" created="Fri, 4 Nov 2016 10:06:11 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{u&apos;username&apos;: u&apos;michaelcahill&apos;, u&apos;name&apos;: u&apos;Michael Cahill&apos;, u&apos;email&apos;: u&apos;michael.cahill@mongodb.com&apos;}
&lt;p&gt;Message: &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-26753&quot; title=&quot;Minor speed regression (13%) and &amp;#39;choppy&amp;#39; performance in 3.4 vs 3.2&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-26753&quot;&gt;&lt;del&gt;SERVER-26753&lt;/del&gt;&lt;/a&gt; Don&apos;t spin on a read-lock in a tight loop. (#3113)&lt;/p&gt;

&lt;ul&gt;
	&lt;li&gt;&lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-26753&quot; title=&quot;Minor speed regression (13%) and &amp;#39;choppy&amp;#39; performance in 3.4 vs 3.2&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-26753&quot;&gt;&lt;del&gt;SERVER-26753&lt;/del&gt;&lt;/a&gt; Don&apos;t spin on a read-lock in a tight loop.&lt;/li&gt;
&lt;/ul&gt;


&lt;p&gt;We could be starving a thread that we are waiting on of CPU.&lt;/p&gt;

&lt;ul&gt;
	&lt;li&gt;Switch to yielding on rwlocks rather than sleeping.&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;Revert the attempt to be clever when spinning on rwlocks.&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;Spin getting a read lock while it is available to readers.&lt;br/&gt;
Branch: mongodb-3.2&lt;br/&gt;
&lt;a href=&quot;https://github.com/wiredtiger/wiredtiger/commit/b90338afdc09c50cf3a321a9778c8e650fc3d6a1&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/wiredtiger/wiredtiger/commit/b90338afdc09c50cf3a321a9778c8e650fc3d6a1&lt;/a&gt;&lt;/li&gt;
&lt;/ul&gt;
</comment>
                            <comment id="1426052" author="xgen-internal-githook" created="Fri, 4 Nov 2016 10:06:04 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{u&apos;username&apos;: u&apos;michaelcahill&apos;, u&apos;name&apos;: u&apos;Michael Cahill&apos;, u&apos;email&apos;: u&apos;michael.cahill@mongodb.com&apos;}
&lt;p&gt;Message: &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-26753&quot; title=&quot;Minor speed regression (13%) and &amp;#39;choppy&amp;#39; performance in 3.4 vs 3.2&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-26753&quot;&gt;&lt;del&gt;SERVER-26753&lt;/del&gt;&lt;/a&gt; Add a call to spin on rwlocks with no active writers  (#3126)&lt;br/&gt;
Branch: mongodb-3.4&lt;br/&gt;
&lt;a href=&quot;https://github.com/wiredtiger/wiredtiger/commit/f418cea41b61f47fda740751495f9f5d39d814fd&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/wiredtiger/wiredtiger/commit/f418cea41b61f47fda740751495f9f5d39d814fd&lt;/a&gt;&lt;/p&gt;</comment>
                            <comment id="1426033" author="xgen-internal-githook" created="Fri, 4 Nov 2016 10:05:53 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{u&apos;username&apos;: u&apos;michaelcahill&apos;, u&apos;name&apos;: u&apos;Michael Cahill&apos;, u&apos;email&apos;: u&apos;michael.cahill@mongodb.com&apos;}
&lt;p&gt;Message: &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-26753&quot; title=&quot;Minor speed regression (13%) and &amp;#39;choppy&amp;#39; performance in 3.4 vs 3.2&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-26753&quot;&gt;&lt;del&gt;SERVER-26753&lt;/del&gt;&lt;/a&gt; Don&apos;t spin on a read-lock in a tight loop. (#3113)&lt;/p&gt;

&lt;ul&gt;
	&lt;li&gt;&lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-26753&quot; title=&quot;Minor speed regression (13%) and &amp;#39;choppy&amp;#39; performance in 3.4 vs 3.2&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-26753&quot;&gt;&lt;del&gt;SERVER-26753&lt;/del&gt;&lt;/a&gt; Don&apos;t spin on a read-lock in a tight loop.&lt;/li&gt;
&lt;/ul&gt;


&lt;p&gt;We could be starving a thread that we are waiting on of CPU.&lt;/p&gt;

&lt;ul&gt;
	&lt;li&gt;Switch to yielding on rwlocks rather than sleeping.&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;Revert the attempt to be clever when spinning on rwlocks.&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;Spin getting a read lock while it is available to readers.&lt;br/&gt;
Branch: mongodb-3.4&lt;br/&gt;
&lt;a href=&quot;https://github.com/wiredtiger/wiredtiger/commit/b90338afdc09c50cf3a321a9778c8e650fc3d6a1&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/wiredtiger/wiredtiger/commit/b90338afdc09c50cf3a321a9778c8e650fc3d6a1&lt;/a&gt;&lt;/li&gt;
&lt;/ul&gt;
</comment>
                            <comment id="1426032" author="xgen-internal-githook" created="Fri, 4 Nov 2016 10:05:52 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{u&apos;username&apos;: u&apos;michaelcahill&apos;, u&apos;name&apos;: u&apos;Michael Cahill&apos;, u&apos;email&apos;: u&apos;michael.cahill@mongodb.com&apos;}
&lt;p&gt;Message: &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-26753&quot; title=&quot;Minor speed regression (13%) and &amp;#39;choppy&amp;#39; performance in 3.4 vs 3.2&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-26753&quot;&gt;&lt;del&gt;SERVER-26753&lt;/del&gt;&lt;/a&gt; Don&apos;t spin on a read-lock in a tight loop. (#3113)&lt;/p&gt;

&lt;ul&gt;
	&lt;li&gt;&lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-26753&quot; title=&quot;Minor speed regression (13%) and &amp;#39;choppy&amp;#39; performance in 3.4 vs 3.2&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-26753&quot;&gt;&lt;del&gt;SERVER-26753&lt;/del&gt;&lt;/a&gt; Don&apos;t spin on a read-lock in a tight loop.&lt;/li&gt;
&lt;/ul&gt;


&lt;p&gt;We could be starving a thread that we are waiting on of CPU.&lt;/p&gt;

&lt;ul&gt;
	&lt;li&gt;Switch to yielding on rwlocks rather than sleeping.&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;Revert the attempt to be clever when spinning on rwlocks.&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;Spin getting a read lock while it is available to readers.&lt;br/&gt;
Branch: mongodb-3.4&lt;br/&gt;
&lt;a href=&quot;https://github.com/wiredtiger/wiredtiger/commit/b90338afdc09c50cf3a321a9778c8e650fc3d6a1&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/wiredtiger/wiredtiger/commit/b90338afdc09c50cf3a321a9778c8e650fc3d6a1&lt;/a&gt;&lt;/li&gt;
&lt;/ul&gt;
</comment>
                            <comment id="1425945" author="xgen-internal-githook" created="Fri, 4 Nov 2016 06:09:44 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{u&apos;username&apos;: u&apos;michaelcahill&apos;, u&apos;name&apos;: u&apos;Michael Cahill&apos;, u&apos;email&apos;: u&apos;michael.cahill@mongodb.com&apos;}
&lt;p&gt;Message: &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-26753&quot; title=&quot;Minor speed regression (13%) and &amp;#39;choppy&amp;#39; performance in 3.4 vs 3.2&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-26753&quot;&gt;&lt;del&gt;SERVER-26753&lt;/del&gt;&lt;/a&gt; Add a call to spin on rwlocks with no active writers  (#3126)&lt;br/&gt;
Branch: develop&lt;br/&gt;
&lt;a href=&quot;https://github.com/wiredtiger/wiredtiger/commit/f418cea41b61f47fda740751495f9f5d39d814fd&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/wiredtiger/wiredtiger/commit/f418cea41b61f47fda740751495f9f5d39d814fd&lt;/a&gt;&lt;/p&gt;</comment>
                            <comment id="1425790" author="ramon.fernandez" created="Fri, 4 Nov 2016 00:29:09 +0000"  >&lt;p&gt;Hi &lt;a href=&quot;https://jira.mongodb.org/secure/ViewProfile.jspa?name=nick%40innsenroute.com&quot; class=&quot;user-hover&quot; rel=&quot;nick@innsenroute.com&quot;&gt;nick@innsenroute.com&lt;/a&gt;, thanks for testing the patch build and glad to hear it addressed this issue.&lt;/p&gt;

&lt;p&gt;If you have other test cases where you see unexpected behavior please open a new SERVER ticket for each so we can take a look &amp;#8211; and remember that all these issues are eligible for &lt;a href=&quot;https://www.mongodb.com/blog/post/announcing-the-mongodb-3-4-bug-hunt&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;Bug Hunt&lt;/a&gt; prizes, so remember to set the &quot;affects version/s&quot; field to the specific release candidate you&apos;re using!&lt;/p&gt;

&lt;p&gt;Thanks,&lt;br/&gt;
Ram&#243;n.&lt;/p&gt;</comment>
                            <comment id="1425755" author="nick@innsenroute.com" created="Thu, 3 Nov 2016 22:42:13 +0000"  >&lt;p&gt;&lt;a href=&quot;https://jira.mongodb.org/secure/ViewProfile.jspa?name=michael.cahill&quot; class=&quot;user-hover&quot; rel=&quot;michael.cahill&quot;&gt;michael.cahill&lt;/a&gt; - yes, performance is flat as a pancake now. Thanks for looking into it! I have another test which simply uses the bulk insert api instead of single inserts (same test as above). This test appears to be really taxing on Mongo/WT and the performance is often worse than single-insert mode.&lt;/p&gt;

&lt;p&gt;Would you recommend posting this to JIRA or perhaps to the google groups instead?&lt;/p&gt;

&lt;p&gt;Thanks!&lt;/p&gt;</comment>
                            <comment id="1424772" author="michael.cahill" created="Thu, 3 Nov 2016 01:41:11 +0000"  >&lt;p&gt;&lt;a href=&quot;https://jira.mongodb.org/secure/ViewProfile.jspa?name=nick%40innsenroute.com&quot; class=&quot;user-hover&quot; rel=&quot;nick@innsenroute.com&quot;&gt;nick@innsenroute.com&lt;/a&gt;, there is a build here:&lt;/p&gt;

&lt;p&gt;  &lt;a href=&quot;https://evergreen.mongodb.com/version/5819599d3ff1221cb4000075&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://evergreen.mongodb.com/version/5819599d3ff1221cb4000075&lt;/a&gt;&lt;/p&gt;

&lt;p&gt;The Windows binaries are:&lt;/p&gt;

&lt;p&gt;  &lt;a href=&quot;https://s3.amazonaws.com/mciuploads/mongodb-mongo-v3.2/windows-64-2k8-ssl/819946a376ba70cb6451a61695dcce42084f3863/binaries/mongo-mongodb_mongo_v3.2_windows_64_2k8_ssl_819946a376ba70cb6451a61695dcce42084f3863_16_11_02_03_14_24.zip&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://s3.amazonaws.com/mciuploads/mongodb-mongo-v3.2/windows-64-2k8-ssl/819946a376ba70cb6451a61695dcce42084f3863/binaries/mongo-mongodb_mongo_v3.2_windows_64_2k8_ssl_819946a376ba70cb6451a61695dcce42084f3863_16_11_02_03_14_24.zip&lt;/a&gt;&lt;/p&gt;

&lt;p&gt;Please let me know if this resolves the spiky performance issues.&lt;/p&gt;</comment>
                            <comment id="1423623" author="nick@innsenroute.com" created="Wed, 2 Nov 2016 03:04:33 +0000"  >&lt;p&gt;@Michael Cahill - sure. Send me a link and I&apos;ll try it out. Thanks!&lt;/p&gt;</comment>
                            <comment id="1423622" author="michael.cahill" created="Wed, 2 Nov 2016 03:03:20 +0000"  >&lt;p&gt;&lt;a href=&quot;https://jira.mongodb.org/secure/ViewProfile.jspa?name=nick%40innsenroute.com&quot; class=&quot;user-hover&quot; rel=&quot;nick@innsenroute.com&quot;&gt;nick@innsenroute.com&lt;/a&gt;, we&apos;ve figured out at least part of what is going on here: WiredTiger was spinning in a tight loop under some circumstances, leading to CPU starvation.  A change has been merged into the WiredTiger tree, and will now go through more testing before being merged into MongoDB.&lt;/p&gt;

&lt;p&gt;If you&apos;d like to try out the change in the meantime to confirm that it improves things for you, please let me know and I&apos;ll prepare a build.&lt;/p&gt;</comment>
                            <comment id="1423620" author="xgen-internal-githook" created="Wed, 2 Nov 2016 02:59:01 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{u&apos;username&apos;: u&apos;michaelcahill&apos;, u&apos;name&apos;: u&apos;Michael Cahill&apos;, u&apos;email&apos;: u&apos;michael.cahill@mongodb.com&apos;}
&lt;p&gt;Message: &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-26753&quot; title=&quot;Minor speed regression (13%) and &amp;#39;choppy&amp;#39; performance in 3.4 vs 3.2&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-26753&quot;&gt;&lt;del&gt;SERVER-26753&lt;/del&gt;&lt;/a&gt; Don&apos;t spin on a read-lock in a tight loop. (#3113)&lt;/p&gt;

&lt;ul&gt;
	&lt;li&gt;&lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-26753&quot; title=&quot;Minor speed regression (13%) and &amp;#39;choppy&amp;#39; performance in 3.4 vs 3.2&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-26753&quot;&gt;&lt;del&gt;SERVER-26753&lt;/del&gt;&lt;/a&gt; Don&apos;t spin on a read-lock in a tight loop.&lt;/li&gt;
&lt;/ul&gt;


&lt;p&gt;We could be starving a thread that we are waiting on of CPU.&lt;/p&gt;

&lt;ul&gt;
	&lt;li&gt;Switch to yielding on rwlocks rather than sleeping.&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;Revert the attempt to be clever when spinning on rwlocks.&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;Spin getting a read lock while it is available to readers.&lt;br/&gt;
Branch: develop&lt;br/&gt;
&lt;a href=&quot;https://github.com/wiredtiger/wiredtiger/commit/b90338afdc09c50cf3a321a9778c8e650fc3d6a1&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/wiredtiger/wiredtiger/commit/b90338afdc09c50cf3a321a9778c8e650fc3d6a1&lt;/a&gt;&lt;/li&gt;
&lt;/ul&gt;
</comment>
                            <comment id="1419799" author="nick@innsenroute.com" created="Thu, 27 Oct 2016 19:00:00 +0000"  >&lt;p&gt;@Michael Cahill, I can set you up with my workload - I&apos;ve sent you an email.&lt;/p&gt;</comment>
                            <comment id="1419141" author="michael.cahill" created="Thu, 27 Oct 2016 05:34:39 +0000"  >&lt;p&gt;&lt;a href=&quot;https://jira.mongodb.org/secure/ViewProfile.jspa?name=nick%40innsenroute.com&quot; class=&quot;user-hover&quot; rel=&quot;nick@innsenroute.com&quot;&gt;nick@innsenroute.com&lt;/a&gt; thanks for the updated data.  What we see in the diagnostic data is that there&apos;s nothing obviously going wrong when these spikes occur: sometimes they correlate with checkpoints but sometimes they happen independent of checkpoints, operations aren&apos;t waiting on I/O, the cache isn&apos;t full, etc.&lt;/p&gt;

&lt;p&gt;There &lt;b&gt;is&lt;/b&gt; a strong correlation with spikes in read-lock operations &amp;#8211; in other words, it looks like we&apos;re spinning trying to get shared access to something.  I have some ideas about what could be causing this because we made a change to the way we access the data structure representing the transaction table.  If it&apos;s easy for me to run your workload, that would be great, otherwise we&apos;ll try to reproduce this ourselves.&lt;/p&gt;</comment>
                            <comment id="1418401" author="nick@innsenroute.com" created="Wed, 26 Oct 2016 16:24:42 +0000"  >&lt;p&gt;@Alexander Gorrod: &lt;/p&gt;
&lt;ul class=&quot;alternate&quot; type=&quot;square&quot;&gt;
	&lt;li&gt;Replication is not enabled&lt;/li&gt;
	&lt;li&gt;journaling is enabled&lt;/li&gt;
	&lt;li&gt;I&apos;m using the c# driver defaults&lt;/li&gt;
	&lt;li&gt;The write load should be very consistent, as is the read load.&lt;/li&gt;
&lt;/ul&gt;


&lt;p&gt;I can provide a copy of my workload, although I think someone over there already has it.&lt;/p&gt;</comment>
                            <comment id="1418393" author="nick@innsenroute.com" created="Wed, 26 Oct 2016 16:21:24 +0000"  >&lt;p&gt;Attaching the same run for 3.2.10. I&apos;m seeing similar behavior in 3.2.10 as 3.4rc1, although perhaps the spikes are not happening quite as often.&lt;/p&gt;</comment>
                            <comment id="1417797" author="alexander.gorrod" created="Wed, 26 Oct 2016 05:47:26 +0000"  >&lt;p&gt;Hi &lt;a href=&quot;https://jira.mongodb.org/secure/ViewProfile.jspa?name=nick%40innsenroute.com&quot; class=&quot;user-hover&quot; rel=&quot;nick@innsenroute.com&quot;&gt;nick@innsenroute.com&lt;/a&gt;, thanks for the report and sorry about the performance regression in your workload. We have done some analysis on the data you uploaded, and the cause of the behavior difference isn&apos;t obvious.&lt;/p&gt;

&lt;p&gt;We did notice that the 3.2 statistics are running MongoDB 3.2.9, where you said it was running 3.2.10. There are significant changes to WiredTiger between 3.2.9 and 3.2.10 - could you re-run the test with 3.2.10 and let us know the results?&lt;/p&gt;

&lt;p&gt;It would also be useful if you can describe the configuration and workload, including:&lt;/p&gt;
&lt;ul&gt;
	&lt;li&gt;Whether replication is enabled.&lt;/li&gt;
	&lt;li&gt;Whether journaling is enabled.&lt;/li&gt;
	&lt;li&gt;Whether you are doing j:true writes.&lt;/li&gt;
	&lt;li&gt;How stable the incoming requests are (it appears as though there are periodic increases in query load for example).&lt;/li&gt;
&lt;/ul&gt;


&lt;blockquote&gt;&lt;p&gt;I also noticed that 3.4 was using less memory. With WT capped at 3GB, it was sitting at ~2.7 vs ~3.2 for 3.2. Are you using the more aggressive decommit in 3.4?&lt;/p&gt;&lt;/blockquote&gt;

&lt;p&gt;We have made a lot of changes to how WiredTiger manages the cache recently, some of those changes are aimed at reducing the amount of memory allocator fragmentation we see (i.e: allocator overhead). It is good to know that the changes have had the desired affect. To explain why the usage falls below 3GB overall, WiredTiger attempts to maintain used cache at 80% of the configured maximum (2.4GB for your configuration), and I can see from the statistics that cache usage is being maintained close to that. The other 300MB you observe is used for allocations outside of WiredTiger and fragmentation in the allocator cache.&lt;/p&gt;</comment>
                            <comment id="1416203" author="dan@10gen.com" created="Mon, 24 Oct 2016 21:07:14 +0000"  >&lt;p&gt;Thanks for the report Nick.  We&apos;ll take a look at the diagnostic data.&lt;/p&gt;</comment>
                            <comment id="1416057" author="nick@innsenroute.com" created="Mon, 24 Oct 2016 19:35:38 +0000"  >&lt;p&gt;I also noticed that 3.4 was using less memory. With WT capped at 3GB, it was sitting at ~2.7 vs ~3.2 for 3.2. Are you using the more aggressive decommit in 3.4?&lt;/p&gt;</comment>
                    </comments>
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