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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-32711] WiredTiger scan performance for the insert benchmark</title>
                <link>https://jira.mongodb.org/browse/SERVER-32711</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;This covers full scan performance during the &lt;a href=&quot;http://smalldatum.blogspot.com/2017/06/the-insert-benchmark.html&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;insert benchmark&lt;/a&gt;. It is related to &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-32707&quot; title=&quot;WiredTiger performance with the insert benchmark&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-32707&quot;&gt;SERVER-32707&lt;/a&gt; which documents problems during the load with the insert benchmark. The scan phase of the insert benchmark does a full scan per collection. Here I run the insert benchmark with 16 clients and either 16 collections (client per collection) or 1 collections (all clients share one collection). So the tests are either:&lt;/p&gt;
&lt;ul&gt;
	&lt;li&gt;16 clients each scanning a separate collection&lt;/li&gt;
	&lt;li&gt;1 client scanning one collection&lt;/li&gt;
&lt;/ul&gt;


&lt;p&gt;The test is run in four configurations:&lt;/p&gt;
&lt;ul&gt;
	&lt;li&gt;inMemory-1 - cached database with 16 clients and 1 collection&lt;/li&gt;
	&lt;li&gt;inMemory-16 - cached database with 16 clients and 16 collections (collection per client)&lt;/li&gt;
	&lt;li&gt;ioBound-none - database larger than memory, 16 clients, no compression&lt;/li&gt;
	&lt;li&gt;ioBound-zlib - database larger than memory, 16 clients, zlib compression&lt;/li&gt;
&lt;/ul&gt;


&lt;p&gt;While I tested nine different mongo.conf variations they all provide similar scan performance so I only share results for the first configuration.&lt;/p&gt;

&lt;p&gt;The collection(s) has/have 3 secondary indexes in addition to the index on _id&lt;/p&gt;

&lt;p&gt;This test does 5 rounds of full scans. The work done per round is:&lt;/p&gt;
&lt;ol&gt;
	&lt;li&gt;full scan of the index on _id. In some cases this query is slower because dirty pages will be flushed while the query is in progress&lt;/li&gt;
	&lt;li&gt;full scan of the first secondary index&lt;/li&gt;
	&lt;li&gt;full scan of the second secondary index&lt;/li&gt;
	&lt;li&gt;full scan of the third secondary index&lt;/li&gt;
	&lt;li&gt;full scan of the index on _id&lt;/li&gt;
&lt;/ol&gt;


&lt;p&gt;The queries are written to do a full scan but return 0 rows. Alas, that hits a perf bug in MongoDB &amp;#8211; see &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-31078&quot; title=&quot;Query planning is very slow during multiplanning when result set is empty&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-31078&quot;&gt;SERVER-31078&lt;/a&gt;. It looks like this makes such queries take ~1.5x longer than needed, but for the sake of this bug I will round up and claim it makes queries take 2X longer than needed. &lt;/p&gt;</description>
                <environment></environment>
        <key id="483184">SERVER-32711</key>
            <summary>WiredTiger scan performance for the insert benchmark</summary>
                <type id="4" iconUrl="https://jira.mongodb.org/secure/viewavatar?size=xsmall&amp;avatarId=14710&amp;avatarType=issuetype">Improvement</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-perf">Backlog - Performance Team</assignee>
                                    <reporter username="mdcallag">Mark Callaghan</reporter>
                        <labels>
                    </labels>
                <created>Tue, 16 Jan 2018 03:44:54 +0000</created>
                <updated>Tue, 6 Dec 2022 03:41:32 +0000</updated>
                                                                            <component>WiredTiger</component>
                                        <votes>0</votes>
                                    <watches>20</watches>
                                                                                                                <comments>
                            <comment id="1774692" author="mdcallag" created="Tue, 16 Jan 2018 04:05:33 +0000"  >&lt;p&gt;This table lists aggregate query throughput in millions of rows scanned per second for each configuration. The first group is for the in-memory test with 16 clients and 16 collections. The second group is for the IO-bound test with 16 clients and 16 collections. The last group is for the in-memory test with one collection.&lt;/p&gt;
&lt;ul&gt;
	&lt;li&gt;InnoDB gets between 10X and 20X more throughput on the concurrent in-memory scan&lt;/li&gt;
	&lt;li&gt;InnoDB gets between 3X and 8X more throughput on the concurrent IO-bound scans&lt;/li&gt;
	&lt;li&gt;WiredTiger gets the same scan throughput on the concurrent tests &amp;#8211; both IO-bound and in-memory &amp;#8211; because it is extremely CPU bound&lt;/li&gt;
&lt;/ul&gt;


&lt;p/&gt;
&lt;div id=&quot;syntaxplugin&quot; class=&quot;syntaxplugin&quot; style=&quot;border: 1px dashed #bbb; border-radius: 5px !important; overflow: auto; max-height: 30em;&quot;&gt;
&lt;table cellspacing=&quot;0&quot; cellpadding=&quot;0&quot; border=&quot;0&quot; width=&quot;100%&quot; style=&quot;font-size: 1em; line-height: 1.4em !important; font-weight: normal; font-style: normal; color: black;&quot;&gt;
		&lt;tbody &gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;  margin-top: 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;1       2       3       4       5      configuration&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt; 5.952   2.941   3.906   3.012   5.952  inMemory-16-WiredTiger&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;55.555  55.555  55.555  62.500  62.500  inMemory-16-InnoDB&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;-&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt; 5.633   2.789   3.478   2.785   5.681  ioBound-16-WiredTiger&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;14.285  26.315  24.691  19.801  48.780  ioBound-16-InnoDB&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;-&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   margin-bottom: 10px;  width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;1.612   0.415   0.533   0.424   1.851  inMemory-1&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
			&lt;/tbody&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;p/&gt;

&lt;p&gt;One of the metrics that I compute during this test is CPU overhead per row scanned and that value is 10X larger for WiredTiger than for InnoDB.&lt;/p&gt;</comment>
                    </comments>
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                                            <outwardlinks description="related to">
                                        <issuelink>
            <issuekey id="483147">SERVER-32707</issuekey>
        </issuelink>
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