lkml.org 
[lkml]   [2013]   [Oct]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 092/104] mm: fix aio performance regression for database caused by THP
On Mon, Sep 30, 2013 at 08:00:02AM -0700, Greg Kroah-Hartman wrote:
> On Mon, Sep 30, 2013 at 07:31:35AM -0600, Khalid Aziz wrote:
> > On 09/30/2013 07:26 AM, Greg Kroah-Hartman wrote:
> > > On Mon, Sep 30, 2013 at 03:14:52PM +0200, Jack Wang wrote:
> > >> On 09/30/2013 12:11 PM, Luis Henriques wrote:
> > >>> 3.5.7.22 -stable review patch. If anyone has any objections, please let me know.
> > >>>
> > >>> ------------------
> > >>>
> > >>> From: Khalid Aziz <khalid.aziz@oracle.com>
> > >>>
> > >>> commit 7cb2ef56e6a8b7b368b2e883a0a47d02fed66911 upstream.
> > >>>
> > >>> I am working with a tool that simulates oracle database I/O workload.
> > >>> This tool (orion to be specific -
> > >>> <http://docs.oracle.com/cd/E11882_01/server.112/e16638/iodesign.htm#autoId24>)
> > >>> allocates hugetlbfs pages using shmget() with SHM_HUGETLB flag. It then
> > >>> does aio into these pages from flash disks using various common block
> > >>> sizes used by database. I am looking at performance with two of the most
> > >>> common block sizes - 1M and 64K. aio performance with these two block
> > >>> sizes plunged after Transparent HugePages was introduced in the kernel.
> > >>> Here are performance numbers:
> > >>>
> > >>> pre-THP 2.6.39 3.11-rc5
> > >>> 1M read 8384 MB/s 5629 MB/s 6501 MB/s
> > >>> 64K read 7867 MB/s 4576 MB/s 4251 MB/s
> > >>>
> > >>> I have narrowed the performance impact down to the overheads introduced by
> > >>> THP in __get_page_tail() and put_compound_page() routines. perf top shows
> > >>>> 40% of cycles being spent in these two routines. Every time direct I/O
> > >>> to hugetlbfs pages starts, kernel calls get_page() to grab a reference to
> > >>> the pages and calls put_page() when I/O completes to put the reference
> > >>> away. THP introduced significant amount of locking overhead to get_page()
> > >>> and put_page() when dealing with compound pages because hugepages can be
> > >>> split underneath get_page() and put_page(). It added this overhead
> > >>> irrespective of whether it is dealing with hugetlbfs pages or transparent
> > >>> hugepages. This resulted in 20%-45% drop in aio performance when using
> > >>> hugetlbfs pages.
> > >>>
> > >>> Since hugetlbfs pages can not be split, there is no reason to go through
> > >>> all the locking overhead for these pages from what I can see. I added
> > >>> code to __get_page_tail() and put_compound_page() to bypass all the
> > >>> locking code when working with hugetlbfs pages. This improved performance
> > >>> significantly. Performance numbers with this patch:
> > >>>
> > >>> pre-THP 3.11-rc5 3.11-rc5 + Patch
> > >>> 1M read 8384 MB/s 6501 MB/s 8371 MB/s
> > >>> 64K read 7867 MB/s 4251 MB/s 6510 MB/s
> > >>>
> > >>> Performance with 64K read is still lower than what it was before THP, but
> > >>> still a 53% improvement. It does mean there is more work to be done but I
> > >>> will take a 53% improvement for now.
> > >>>
> > >>> Please take a look at the following patch and let me know if it looks
> > >>> reasonable.
> > >>>
> > >>> [akpm@linux-foundation.org: tweak comments]
> > >>> Signed-off-by: Khalid Aziz <khalid.aziz@oracle.com>
> > >>> Cc: Pravin B Shelar <pshelar@nicira.com>
> > >>> Cc: Christoph Lameter <cl@linux.com>
> > >>> Cc: Andrea Arcangeli <aarcange@redhat.com>
> > >>> Cc: Johannes Weiner <hannes@cmpxchg.org>
> > >>> Cc: Mel Gorman <mel@csn.ul.ie>
> > >>> Cc: Rik van Riel <riel@redhat.com>
> > >>> Cc: Minchan Kim <minchan@kernel.org>
> > >>> Cc: Andi Kleen <andi@firstfloor.org>
> > >>> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> > >>> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
> > >>> [ luis: backported to 3.5: adjusted context ]
> > >>> Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
> > >> Hi Greg,
> > >>
> > >> I suppose this patch also needed for 3.4, right?
> > >
> > > As it didn't originally apply there, I didn't apply it.
> > >
> > > If people think it should be applicable for 3.4, I'll take it.
> > >
> > > thanks,
> > >
> > > greg k-h
> > >
> >
> > Hi Greg,
> >
> > I did send you a backported version of this patch to apply to 3.0, 3.2
> > and 3.4 last Monday and cc'd stable@vger.kernel.org. That patch should
> > apply cleanly to those three kernels.
>
> Ah, you didn't specifically say that in the patch, so I just thought you
> were reminding me to apply it to the 3.10 and 3.11 trees. Please be
> more explicit in the future.
>
> I'll queue it up for the next round of stable kernels after this one.

And I've lost it, I can't find it in my archives anywhere. Sorry about
that, can you resend it please?

thanks,

greg k-h


\
 
 \ /
  Last update: 2013-10-03 05:01    [W:0.088 / U:2.728 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site