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https://issues.apache.org/jira/browse/YARN-11675?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17842004#comment-17842004
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ASF GitHub Bot commented on YARN-11675:
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brumi1024 merged PR #6760:
URL: https://github.com/apache/hadoop/pull/6760
> Update MemoryResourceHandler implementation for cgroup v2 support
> -----------------------------------------------------------------
>
> Key: YARN-11675
> URL: https://issues.apache.org/jira/browse/YARN-11675
> Project: Hadoop YARN
> Issue Type: Sub-task
> Reporter: Benjamin Teke
> Assignee: Peter Szucs
> Priority: Major
> Labels: pull-request-available
>
> cgroup v2 has some changes in various controllers (some changed their
> functionality, some were removed). This task is about updating
> MemoryResourceHandler's
> [implementation|https://github.com/apache/hadoop/blob/d336227e5c63a70db06ac26697994c96ed89d230/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/linux/resources/CGroupsMemoryResourceHandlerImpl.java#L47-L46].
> h3. *Differences in the controls comparing to cgroup v1:*
> h3. Hard limit on memory
> {_}memory{_}.{_}limit_in_bytes{_} control is replaced with _memory.max_
> h3. Soft limit on memory
> {_}memory{_}.soft_{_}limit_in_bytes{_} control is replaced with _memory.low_
> Detailed descriptions about the memory controls can be found in the official
> [cgroup v2 documentation|https://docs.kernel.org/admin-guide/cgroup-v2.html].
> h3. Swappiness
> _memory.swappiness_ has been removed from the available cgroup v2 controls.
> Quoting [redhat documentation|https://access.redhat.com/solutions/103833]:
> {quote}Swappiness is a property for the Linux kernel that changes the balance
> between swapping out runtime memory, as opposed to dropping pages from the
> system page cache. Swappiness can be set to values between 0 and 100,
> inclusive. A low value means the kernel will try to avoid swapping as much as
> possible where a higher value instead will make the kernel aggressively try
> to use swap space.
> {quote}
> Referring [this|https://github.com/opencontainers/runtime-spec/issues/1005]
> case study we found that most of the time swappiness didn't work as expected
> as it mostly depends on the I/O balance of the system, so it is no longer
> available in cgroup v2.
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