linux-kernel - Re: [patch 00/52] vfs scalability patches updated

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20100701172317.GB1830@laptop>
Date:	Fri, 2 Jul 2010 03:23:17 +1000
From:	Nick Piggin <npiggin@...e.de>
To:	Dave Chinner <david@...morbit.com>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	John Stultz <johnstul@...ibm.com>,
	Frank Mayhar <fmayhar@...gle.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [patch 00/52] vfs scalability patches updated

On Wed, Jun 30, 2010 at 10:40:49PM +1000, Nick Piggin wrote:
> But actually it's not all for scalability. I have some follow on patches
> (that require RCU inodes, among other things) that actually improve
> single threaded performance significnatly. git diff workload IIRC was
> several % improved from speeding up stat(2).

I rewrote the store-free path walk patch that goes on top of this
patchset (it's now much cleaner and more optimised, I'll post a patch
soonish). It is quicker than I remembered.

A single thread running stat(2) in a loop on a file "./file" has the
following cost (on an 2s8c Barcelona):

2.6.35-rc3	595 ns/op
patched		336 ns/op

stat(2) takes 56% the time with patches. It's something like 13 fewer
atomic operations per syscall.

What's that good for? A single threaded, cached `git diff` on the linux
kernel tree takes just 81% of the time after the vfs patches (0.27s vs
0.33s).

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/