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* [PATCH v5.1 00/14] crc32c: Add faster algorithm and self-test code
@ 2011-11-28 22:36 Darrick J. Wong
  2011-11-28 22:37 ` [PATCH 01/14] removed two instances of trailing whitespaces Darrick J. Wong
                   ` (14 more replies)
  0 siblings, 15 replies; 17+ messages in thread
From: Darrick J. Wong @ 2011-11-28 22:36 UTC (permalink / raw)
  To: Andrew Morton, Herbert Xu, Darrick J. Wong
  Cc: Theodore Tso, Joakim Tjernlund, Bob Pearson, linux-kernel,
	Andreas Dilger, linux-crypto, linux-fsdevel, Mingming Cao,
	linux-ext4

Hi all,

This patchset (re)uses Bob Pearson's crc32 slice-by-8 code to stamp out a
software crc32c implementation.  It removes the crc32c implementation in
crypto/ in favor of using the stamped-out one in lib/.  There is also a change
to Kconfig so that the kernel builder can pick an implementation best suited
for the hardware.

The motivation for this patchset is that I am working on adding full metadata
checksumming to ext4.  As far as performance impact of adding checksumming
goes, I see nearly no change with a standard mail server ffsb simulation.  On a
test that involves only file creation and deletion and extent tree writes, I
see a drop of about 50 pcercent with the current kernel crc32c implementation;
this improves to a drop of about 20 percent with the enclosed crc32c code.

When metadata is usually a small fraction of total IO, this new implementation
doesn't help much because metadata is usually a small fraction of total IO.
However, when we are doing IO that is almost all metadata (such as rm -rf'ing a
tree), then this patch speeds up the operation substantially.

Incidentally, given that iscsi, sctp, and btrfs also use crc32c, this patchset
should improve their speed as well.  I have not yet quantified that, however.
This latest submission combines Bob's patches from late August 2011 with mine
so that they can be one coherent patch set.  Please excuse my inability to
combine some of the patches; I've been advised to leave Bob's patches alone and
build atop them instead. :/

Since the last posting, I've also collected some crc32c test results on a bunch
of different x86/powerpc/sparc platforms.  The results can be viewed here:
http://goo.gl/sgt3i ; the "crc32-kern-le" and "crc32c" columns describe the
performance of the kernel's current crc32 and crc32c software implementations.
The "crc32c-by8-le" column shows crc32c performance with this patchset applied.
I expect crc32 performance to be roughly the same.

The two _boost columns at the right side of the spreadsheet shows how much
faster the new implementation is over the old one.  As you can see, crc32 rises
substantially, and crc32c experiences a huge increase.  I'm hoping this patch
set meets with everyone's approval and can go in soon.  Herbert Xu didn't
appear to have any strong objections to last month's posting, so I'm wondering
if Andrew has an opinion?

--D

^ permalink raw reply	[flat|nested] 17+ messages in thread

end of thread, other threads:[~2011-12-01 20:12 UTC | newest]

Thread overview: 17+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2011-11-28 22:36 [PATCH v5.1 00/14] crc32c: Add faster algorithm and self-test code Darrick J. Wong
2011-11-28 22:37 ` [PATCH 01/14] removed two instances of trailing whitespaces Darrick J. Wong
2011-11-28 22:37 ` [PATCH 02/14] Moved a long comment from lib/crc32.c to Documentation/crc32.txt Darrick J. Wong
2011-11-28 22:37 ` [PATCH 03/14] Replaced the unit test provided in crc32.c, which doesn't have a Darrick J. Wong
2011-11-28 22:37 ` [PATCH 04/14] Replace 2D array references by pointer references in loops Darrick J. Wong
2011-11-28 22:37 ` [PATCH 05/14] Misc cleanup of lib/crc32.c and related files Darrick J. Wong
2011-11-28 22:37 ` [PATCH 06/14] crc32.c in its original version freely mixed u32, __le32 and __be32 types Darrick J. Wong
2011-11-28 22:37 ` [PATCH 07/14] crc32.c provides a choice of one of several algorithms for Darrick J. Wong
2011-11-28 22:37 ` [PATCH 08/14] add slicing-by-8 algorithm to the existing Darrick J. Wong
2011-11-28 22:38 ` [PATCH 09/14] Add two changes that improve the performance of x86 systems Darrick J. Wong
2011-11-28 22:38 ` [PATCH 10/14] Some final changes Darrick J. Wong
2011-11-28 22:38 ` [PATCH 11/14] crc32: Bolt on crc32c Darrick J. Wong
2011-11-28 22:38 ` [PATCH 12/14] crypto: crc32c should use library implementation Darrick J. Wong
2011-11-28 22:38 ` [PATCH 13/14] crc32: Add self-test code for crc32c Darrick J. Wong
2011-11-28 22:38 ` [PATCH 14/14] crc32: Select an algorithm via kconfig Darrick J. Wong
2011-11-30 22:29 ` [PATCH v5.1 00/14] crc32c: Add faster algorithm and self-test code Andrew Morton
2011-12-01 20:12   ` Darrick J. Wong

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