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    <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>[JAVA-2174] Read throughput for a small working set memory </title>
                <link>https://jira.mongodb.org/browse/JAVA-2174</link>
                <project id="10006" key="JAVA">Java Driver</project>
                    <description>&lt;p&gt;I believe mongo is supposed to cache rows in memory and simply return results from memory when the working set size is small. I wrote a simple Java client that creates a simple collection with an indexed primary key and a single string field and inserts just one record into the collection, and then repeatedly queries for that record&apos;s field using findOne.&lt;/p&gt;

&lt;p&gt;The maximum throughput I get with many threads for the above workload is just ~15K/s on a 2-core machine. I clearly can write an in-memory hashmap based cache that can serve reads at nearly ~2 million/s by returning non-dirty entries directly from memory. How can I make mongo do the same? Isn&apos;t it automatically supposed to do this optimization? Or is it?&lt;/p&gt;

&lt;p&gt;I tried using both mmap and wiredtiger but the read throughput hardly changes. All I need is a big map that automatically pages to disk in the background. Can mongo do this?&lt;/p&gt;


&lt;p&gt;PS: Apologies if this is not the right forum for such questions. I tried stackoverflow and dba.stackexchange but didn&apos;t get any answers.&lt;/p&gt;</description>
                <environment></environment>
        <key id="281845">JAVA-2174</key>
            <summary>Read throughput for a small working set memory </summary>
                <type id="3" iconUrl="https://jira.mongodb.org/secure/viewavatar?size=xsmall&amp;avatarId=14718&amp;avatarType=issuetype">Task</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="-1">Unassigned</assignee>
                                    <reporter username="avenka">V. Arun</reporter>
                        <labels>
                    </labels>
                <created>Fri, 22 Apr 2016 20:00:06 +0000</created>
                <updated>Wed, 11 Sep 2019 19:13:41 +0000</updated>
                            <resolved>Mon, 25 Apr 2016 18:45:26 +0000</resolved>
                                    <version>0.8</version>
                    <version>3.0.0</version>
                                                    <component>Performance</component>
                                        <votes>0</votes>
                                    <watches>2</watches>
                                                                                                                <comments>
                            <comment id="1245795" author="jeff.yemin" created="Mon, 25 Apr 2016 18:44:38 +0000"  >&lt;p&gt;Please link to the StackOverflow question and we&apos;ll see if we can get someone to take a look at it.  &lt;/p&gt;
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