linux-kernel - Re: [PATCH 1/2][RESEND] improve generic_file_buffered

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] [day] [month] [year] [list]

Message-ID: <20070907193836.GB3023@infradead.org>
Date:	Fri, 7 Sep 2007 20:38:36 +0100
From:	Christoph Hellwig <hch@...radead.org>
To:	Bernd Schubert <bs@...eap.de>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2][RESEND] improve generic_file_buffered_write()

On Fri, Sep 07, 2007 at 08:52:38PM +0200, Bernd Schubert wrote:
> No further response to our patches yet, so we are sending them again, 
> re-diffed against 2.6.23-rc5
> 
> Hi,
> 
> recently we discovered writing to a nfs-exported lustre filesystem is rather 
> slow (20-40 MB/s writing, but over 200 MB/s reading).
> 
> As I already explained on the nfs mailing list, this happens since there is an 
> offset on the very first page due to the nfs header.
> 
> http://sourceforge.net/mailarchive/forum.php?thread_name=200708312003.30446.bernd-schubert%40gmx.de&forum_name=nfs
> 
> While this especially effects lustre, Olaf Kirch also noticed it on another 
> filesystem before and wrote a nfs patch for it. This patch has two 
> disadvantages  - it requires to move all data within the pages, IMHO rather 
> cpu time consuming, furthermore, it presently causes data corruption when 
> more than one nfs thread is running.
> 
> After thinking it over and over again we (Goswin and I) believe it would be 
> best to improve generic_file_buffered_write().
> If there is sufficient data now, as it is usual for aio writes, 
> generic_file_buffered_write() will now fill each page as much as possible and 
> only then prepare/commit it. Before generic_file_buffered_write() commited 
> chunks of pages even though there were still more data.

While the idea is sound in general the code your touching is almost entirely
gone in -mm and hopefully in 2.6.24.  Can you take a look at the Nick's changes
in -mm that introduce  begin_write and end_write methods replacing prepare_write
and commit_write and see if they improve your situation already.  If not they
should at least provide a framework to deal with it in a slightly cleaner way.

-
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/