linux-kernel - Re: [RFC] readdirplus implementations: xgetdents vs dirreadahead syscalls

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Date:	Fri, 25 Jul 2014 10:52:57 -0700
From:	Zach Brown <zab@...hat.com>
To:	Abhijith Das <adas@...hat.com>
Cc:	linux-kernel@...r.kernel.org,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	cluster-devel <cluster-devel@...hat.com>
Subject: Re: [RFC] readdirplus implementations: xgetdents vs dirreadahead
 syscalls

On Fri, Jul 25, 2014 at 01:37:19PM -0400, Abhijith Das wrote:
> Hi all,
> 
> The topic of a readdirplus-like syscall had come up for discussion at last year's
> LSF/MM collab summit. I wrote a couple of syscalls with their GFS2 implementations
> to get at a directory's entries as well as stat() info on the individual inodes.
> I'm presenting these patches and some early test results on a single-node GFS2
> filesystem.
> 
> 1. dirreadahead() - This patchset is very simple compared to the xgetdents() system
> call below and scales very well for large directories in GFS2. dirreadahead() is
> designed to be called prior to getdents+stat operations.

Hmm.  Have you tried plumbing these read-ahead calls in under the normal
getdents() syscalls?

We don't have a filereadahead() syscall and yet we somehow manage to
implement buffered file data read-ahead :).

- z
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