From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f70.google.com (mail-pg0-f70.google.com [74.125.83.70]) by kanga.kvack.org (Postfix) with ESMTP id B4D0F6B0003 for ; Tue, 6 Mar 2018 19:58:02 -0500 (EST) Received: by mail-pg0-f70.google.com with SMTP id l14so241300pgn.21 for ; Tue, 06 Mar 2018 16:58:02 -0800 (PST) Received: from MTA-08-3.privateemail.com (mta-08-3.privateemail.com. [198.54.127.61]) by mx.google.com with ESMTPS id l14si10619202pgc.615.2018.03.06.16.58.01 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 06 Mar 2018 16:58:01 -0800 (PST) Message-ID: <1520384279.1885.2.camel@daniel-wynne-humphries.com> Subject: Re: [Bug 198913] New: Swapping slows to about 20% of expected speed when using multiple swap partitions on separate drives (striping). From: Dan Date: Tue, 06 Mar 2018 16:57:59 -0800 In-Reply-To: <20180306162346.2fad560fa6957480fde918e2@linux-foundation.org> References: <20180306162346.2fad560fa6957480fde918e2@linux-foundation.org> Content-Type: multipart/alternative; boundary="=-+tbatxcqrL6Eq0eeJfXD" Mime-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: bugzilla-daemon@bugzilla.kernel.org, linux-mm@kvack.org, Hugh Dickins --=-+tbatxcqrL6Eq0eeJfXD Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit On Tue, 2018-03-06 at 16:23 -0800, Andrew Morton wrote: > (switched to email.A A Please respond via emailed reply-to-all, not via > the > bugzilla web interface). > > On Sat, 24 Feb 2018 03:56:38 +0000 bugzilla-daemon@bugzilla.kernel.or > g wrote: > > > > > https://bugzilla.kernel.org/show_bug.cgi?id=198913 > > > > A A A A A A A A A A A A Bug ID: 198913 > > A A A A A A A A A A A Summary: Swapping slows to about 20% of expected speed > > when > > A A A A A A A A A A A A A A A A A A A A using multiple swap partitions on separate > > drives > > A A A A A A A A A A A A A A A A A A A A (striping). > > > > ... > > > > Problems > > 1) Linux's swap striping on nine drives performs at only 19.5% of > > the speed of > > a memory-mapped file on a RAID 0 partition on the same nine drives. > > 2) Linux's swap striping performs best with exactly four swap > > partitions and > > performs almost as well with just three partitions. > > > Well that's interesting, thanks.A A Let's get this onto the mm > developers' mailing list and perhaps someone will have a theory.A A And > perhaps Hugh will have a think about it when he returns to the fold. Thanks, if let me know if you need me to run some test code or something. --=-+tbatxcqrL6Eq0eeJfXD Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: 7bit

On Tue, 2018-03-06 at 16:23 -0800, Andrew Morton wrote:

(switched to email.  Please respond via emailed reply-to-all, not via the
bugzilla web interface).

On Sat, 24 Feb 2018 03:56:38 +0000 bugzilla-daemon@bugzilla.kernel.org wrote:


https://bugzilla.kernel.org/show_bug.cgi?id=198913

            Bug ID: 198913
           Summary: Swapping slows to about 20% of expected speed when
                    using multiple swap partitions on separate drives
                    (striping).

...

Problems
1) Linux's swap striping on nine drives performs at only 19.5% of the speed of
a memory-mapped file on a RAID 0 partition on the same nine drives.
2) Linux's swap striping performs best with exactly four swap partitions and
performs almost as well with just three partitions.



Well that's interesting, thanks.  Let's get this onto the mm
developers' mailing list and perhaps someone will have a theory.  And
perhaps Hugh will have a think about it when he returns to the fold.

Thanks, if let me know if you need me to run some test code or something.

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