Re: [RFC] readdirplus implementations: xgetdents vs dirreadahead syscalls

From: Zach Brown
Date: Fri Jul 25 2014 - 13:53:24 EST

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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