Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753615Ab3JCCqE (ORCPT ); Wed, 2 Oct 2013 22:46:04 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:46116 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753317Ab3JCCqB (ORCPT ); Wed, 2 Oct 2013 22:46:01 -0400 Date: Wed, 2 Oct 2013 19:33:11 -0700 From: Greg Kroah-Hartman To: Khalid Aziz Cc: Jack Wang , Luis Henriques , linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com, Pravin B Shelar , Christoph Lameter , Andrea Arcangeli , Johannes Weiner , Mel Gorman , Rik van Riel , Minchan Kim , Andi Kleen , Andrew Morton , Linus Torvalds Subject: Re: [PATCH 092/104] mm: fix aio performance regression for database caused by THP Message-ID: <20131003023311.GA19176@kroah.com> References: <1380535881-9239-1-git-send-email-luis.henriques@canonical.com> <1380535881-9239-93-git-send-email-luis.henriques@canonical.com> <5249794C.5050204@profitbricks.com> <20130930132642.GA7510@kroah.com> <52497D37.9020706@oracle.com> <20130930150002.GA10424@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130930150002.GA10424@kroah.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4908 Lines: 106 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 > > >>> > > >>> commit 7cb2ef56e6a8b7b368b2e883a0a47d02fed66911 upstream. > > >>> > > >>> I am working with a tool that simulates oracle database I/O workload. > > >>> This tool (orion to be specific - > > >>> ) > > >>> 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 > > >>> Cc: Pravin B Shelar > > >>> Cc: Christoph Lameter > > >>> Cc: Andrea Arcangeli > > >>> Cc: Johannes Weiner > > >>> Cc: Mel Gorman > > >>> Cc: Rik van Riel > > >>> Cc: Minchan Kim > > >>> Cc: Andi Kleen > > >>> Signed-off-by: Andrew Morton > > >>> Signed-off-by: Linus Torvalds > > >>> [ luis: backported to 3.5: adjusted context ] > > >>> Signed-off-by: Luis Henriques > > >> 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/