[Ocfs2-tools-devel] [PATCH 0/6] Improve I/O caching (this time with description)

[Joel Becker]

On Thu, May 21, 2009 at 02:26:02PM -0700, Joel Becker wrote:
> Here is a series of patches that improve I/O caching in ocfs2-tools.
> First, we clean up a couple ocfs2_read_blocks() problems.  Then we teach
> the I/O cache code how to do efficient I/Os.  Finally, we get fsck to
> use the cache, and smartly too.

Some numbers:

First, on my PPC LPARs, I have a 47G volume with 1.5G used.  This is
made up of about 5 kernel trees and a couple of extendo files.  It's got
100K inodes.  Existing fsck took 55s, the cached fsck took 32s.  This
system has enough RAM to fit the entire set of suballocators in its I/O
cache, which is the best case.

Next, we move to Sunil's local ocfs2 filesystem.  This filesystem has
been in use for about two years.  He has 410K inodes on that sucker, and
a lot more directories.  Existing fsck took 7m57s.  We then fired off
the cached fsck, and it took 7m17s.  We noted that it was able to get
250M of cache for that run.  Sunil then killed his browser, email
client, and pdf reader.  This enabled us to get an fsck cache of 460M or
so.  That ran in 5m53s.

Joel

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Joel Becker
Principal Software Developer
Oracle
E-mail: joel.becker at oracle.com
Phone: (650) 506-8127