Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755611Ab3I3N0o (ORCPT ); Mon, 30 Sep 2013 09:26:44 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:37867 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755579Ab3I3N0k (ORCPT ); Mon, 30 Sep 2013 09:26:40 -0400 Date: Mon, 30 Sep 2013 06:26:42 -0700 From: Greg Kroah-Hartman To: Jack Wang Cc: Luis Henriques , linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com, Khalid Aziz , 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: <20130930132642.GA7510@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5249794C.5050204@profitbricks.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: 3803 Lines: 83 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 -- 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/