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logging of metadata ops

To: Linux-xfs@xxxxxxxxxxx
Subject: logging of metadata ops
From: Stewart Smith <stewart@xxxxxxxxxxxxxxxx>
Date: Fri, 10 Mar 2006 16:44:57 +0100
Sender: linux-xfs-bounce@xxxxxxxxxxx
on creat(), write(), close() of a file in a directory, at what point is
the creation of the file and its addition to the directory flushed to
the log on disk?

I'm trying to work out what limitations may exist in the "create one
million tables" benchmark that we've been talking about on planetmysql
(and now planet postgresql as well).

For MyISAM this would mean creating 3,000,000 files in a directory.
Currently I'm seeing about 100 table creates/sec (so about 300
files/sec) although bonnie++ shows 716 file creations per second.

So, since MySQL is also writing data to these files, could anything
interesting be happening with the log?

It's also quite possible that MySQL is the bottleneck here and we should
be able to do 716/3=238 table creations/sec.

Although it'd be good to know if that number could be improved upon
simply by tuning the FS log.

(this message comes from the random useless benchmark of the week dept)
Stewart Smith (stewart@xxxxxxxxxxxxxxxx)

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