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Bug 667186 - Add upstream performance enhancement to reduce time page fault handler holds mmap_sem semaphore.
Summary: Add upstream performance enhancement to reduce time page fault handler holds ...
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: kernel
Version: 6.1
Hardware: All
OS: Linux
low
medium
Target Milestone: rc
: ---
Assignee: Larry Woodman
QA Contact: Caspar Zhang
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2011-01-04 18:53 UTC by Larry Woodman
Modified: 2012-02-13 03:58 UTC (History)
2 users (show)

Fixed In Version: kernel-2.6.32-112.el6
Doc Type: Bug Fix
Doc Text:
Clone Of:
Environment:
Last Closed: 2011-05-19 12:40:13 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 Larry Woodman 2011-01-04 18:53:49 UTC 
Description of problem:

mm: retry page fault when blocking on disk transfer
author	Michel Lespinasse <walken>	
	Tue, 26 Oct 2010 21:21:57 +0000 (14:21 -0700)
committer	Linus Torvalds <torvalds>	
	Tue, 26 Oct 2010 23:52:09 +0000 (16:52 -0700)
This change reduces mmap_sem hold times that are caused by waiting for
disk transfers when accessing file mapped VMAs.

It introduces the VM_FAULT_ALLOW_RETRY flag, which indicates that the call
site wants mmap_sem to be released if blocking on a pending disk transfer.
In that case, filemap_fault() returns the VM_FAULT_RETRY status bit and
do_page_fault() will then re-acquire mmap_sem and retry the page fault.

It is expected that the retry will hit the same page which will now be
cached, and thus it will complete with a low mmap_sem hold time.

Tests:

- microbenchmark: thread A mmaps a large file and does random read accesses
  to the mmaped area - achieves about 55 iterations/s. Thread B does
  mmap/munmap in a loop at a separate location - achieves 55 iterations/s
  before, 15000 iterations/s after.

- We are seeing related effects in some applications in house, which show
  significant performance regressions when running without this change.

[akpm: fix warning & crash]
Signed-off-by: Michel Lespinasse <walken>
Acked-by: Rik van Riel <riel>
Acked-by: Linus Torvalds <torvalds>
Cc: Nick Piggin <nickpiggin.au>
Reviewed-by: Wu Fengguang <fengguang.wu>
Cc: Ying Han <yinghan>
Cc: Peter Zijlstra <a.p.zijlstra>
Cc: Ingo Molnar <mingo>
Cc: Thomas Gleixner <tglx>
Acked-by: "H. Peter Anvin" <hpa>
Cc: <linux-arch.org>
Signed-off-by: Andrew Morton <akpm>
Signed-off-by: Linus Torvalds <torvalds>

Version-Release number of selected component (if applicable):


How reproducible:


Steps to Reproduce:
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Actual results:


Expected results:


Additional info:
Comment 2 Larry Woodman 2011-01-04 18:56:13 UTC 
built and tested kernel with nackported upstream patch.  Posted patch to rhkernel-list.

Larry Woodman
Comment 3 RHEL Program Management 2011-01-07 03:48:40 UTC 
This request was evaluated by Red Hat Product Management for
inclusion in the current release of Red Hat Enterprise Linux.
Because the affected component is not scheduled to be updated
in the current release, Red Hat is unfortunately unable to
address this request at this time. Red Hat invites you to
ask your support representative to propose this request, if
appropriate and relevant, in the next release of Red Hat
Enterprise Linux. If you would like it considered as an
exception in the current release, please ask your support
representative.
Comment 4 Suzanne Logcher 2011-01-07 16:21:50 UTC 
This request was erroneously denied for the current release of Red Hat
Enterprise Linux.  The error has been fixed and this request has been
re-proposed for the current release.
Comment 5 RHEL Program Management 2011-01-17 23:00:27 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 Aristeu Rozanski 2011-02-03 16:16:43 UTC 
Patch(es) available on kernel-2.6.32-112.el6
Comment 12 errata-xmlrpc 2011-05-19 12:40:13 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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