Re: [GIT PULL] Ext3 latency fixes

Arjan van de Ven
2009-04-04T23:32:20Z

On Sat, 4 Apr 2009 19:22:22 -0400
Theodore Tso <tytso@mit.edu> wrote:
>
> However, the full latency fixes all the writes are synchronous, so it
> must be the case that the delays are caused by the fact that queue is
> getting implicitly unplugged after the synchronous write, and the
> problem is no longer the mixing of WRITE and WRITE_SYNC requests as
> posted in the commit log for 78f707bf. If we remove the automatic
> unplug for WRITE_SYNC requests, and add an explicit unplug where it is
> needed, that should fix the performance regression for this particular
> sqlite test case.

removing the unplug is bound to be bad; after all we're waiting on the
IO. But maybe it should be "make the unplug a REALLY short time".
At least for rotating storage. For non-rotating .. I'd never wait.

--
Arjan van de Ven Intel Open Source Technology Centre
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