linux-kernel - Re: Improve lseek scalability v3

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Message-ID: <20110916131929.GA27738@dhcp231-156.rdu.redhat.com>
Date:	Fri, 16 Sep 2011 09:19:30 -0400
From:	Josef Bacik <josef@...hat.com>
To:	Matthew Wilcox <matthew@....cx>
Cc:	Andi Kleen <andi@...stfloor.org>, viro@...iv.linux.org.uk,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Improve lseek scalability v3

On Fri, Sep 16, 2011 at 07:00:55AM -0600, Matthew Wilcox wrote:
> On Thu, Sep 15, 2011 at 04:06:46PM -0700, Andi Kleen wrote:
> > Currently generic_file_llseek users synchronize all on the inode i_mutex,
> > which is very heavy handed because it affects even different processes.
> > 
> > This patchkit attempts to make generic_file_llseek (mostly) lockless.
> 
> Yes, but, are there any real workloads which care?  I know will-it-scale
> says that lseek doesn't scale, but any real app which has a seek-heavy
> workload is surely using pread()/pwrite() by now ... after all, they
> were in UNIX98 so they've been a standard for 13 years.
>

Apparently postgresql uses lseek heavily

http://rhaas.blogspot.com/2011/08/linux-and-glibc-scalability.html

Thanks,

Josef 
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