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Bug 647334 (KSMOnTHP) - Allow KSM to split hugepages
Summary: Allow KSM to split hugepages
Keywords:
Status: CLOSED ERRATA
Alias: KSMOnTHP
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: kernel
Version: 6.0
Hardware: Unspecified
OS: Unspecified
medium
medium
Target Milestone: beta
: 6.1
Assignee: Andrea Arcangeli
QA Contact: Zhouping Liu
URL:
Whiteboard:
Depends On:
Blocks: 580954
TreeView+ depends on / blocked
 
Reported: 2010-10-27 22:35 UTC by Glauber Costa
Modified: 2014-01-13 00:01 UTC (History)
8 users (show)

Fixed In Version: kernel-2.6.32-112.el6
Doc Type: Bug Fix
Doc Text:
Clone Of:
Environment:
Last Closed: 2011-05-23 20:27:43 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2011:0542 0 normal SHIPPED_LIVE Important: Red Hat Enterprise Linux 6.1 kernel security, bug fix and enhancement update 2011-05-19 11:58:07 UTC

Description Glauber Costa 2010-10-27 22:35:14 UTC 
For workloads that are hugepage intensive, benefits of KSM are greatly reduced, since it doesn't know how to scan for matches inside hugepages.

KSM should be able to scan for matches inside hugepages, and split them if necessary, allowing for a greater potential for memory compression
Comment 2 Andrea Arcangeli 2011-01-04 15:57:44 UTC 
This build includes all pending THP/VM updates (bug #664772) plus KSM on THP enabled by default. It needs a lot of testing for KSM over THP from QA to be sure it is functionally correct. This is a first version.

http://brewweb.devel.redhat.com/brew/taskinfo?taskID=3006717
Comment 3 Andrea Arcangeli 2011-01-04 17:03:07 UTC 
Patch to enable KSM on THP, posted to rhkernel-list with Message-ID: <20110104165917.GT15823>. Please test kernel in comment #2 mixing THP and KSM. I'm stress testing it here as well.
Comment 4 RHEL Program Management 2011-01-05 08:50:29 UTC 
This request was evaluated by Red Hat Product Management for inclusion
in a Red Hat Enterprise Linux maintenance release. Product Management has 
requested further review of this request by Red Hat Engineering, for potential
inclusion in a Red Hat Enterprise Linux Update release for currently deployed 
products. This request is not yet committed for inclusion in an Update release.
Comment 6 Andrea Arcangeli 2011-01-12 02:36:28 UTC 
I submitted a new build including 4 more fixes from linux-mm, three are migration deadlock fixes (migration is invoked by compaction, all three likely can't trigger on rhel because of .config differences not using SLUB and not enabling preempt but it's safer to have them, especially the one related to preempt), one is a KSM accounting fix needed to pass a ltp testsuite test from Qian. So if you test KSM over THP it's better to test everything at once.

The KSM over THP patch posted as in comment #3 is still valid and unchanged, no problem so far. The changes in this build are irrelevant to THP over KSM but I'd like those last changes to get the most testing possible too. Thanks!

http://brewweb.devel.redhat.com/brew/taskinfo?taskID=3025030
Comment 7 Andrea Arcangeli 2011-01-13 19:14:01 UTC 
3 patches pending (two big and hugetlbfs related) have been merged in -97 and thanks to KSM over THP, the madvise(MADV_*HUGEPAGE) isn't necessary anymore. So I created a new build on top of -97 kernel with only these additional patches left to test:

compound_lock_irqsave
recommended-min_free_kbytes
khugepaged-mmap_sem
compound_get_put_fix
swapin-rmap-exclusive
ksm-on-thp
ksm-lru-drain
migrate-anon_vma-lock
migrate-anon_vma-lock-hugetlb
migrate-lock_page-readahead
compound_trans_head

http://brewweb.devel.redhat.com/brew/taskinfo?taskID=3032335
Comment 14 Aristeu Rozanski 2011-02-03 16:16:46 UTC 
Patch(es) available on kernel-2.6.32-112.el6
Comment 18 errata-xmlrpc 2011-05-23 20:27:43 UTC 
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.

http://rhn.redhat.com/errata/RHSA-2011-0542.html
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