From: | "Curtis Faith" <curtis(at)galtair(dot)com> |
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To: | "Neil Conway" <neilc(at)samurai(dot)com> |
Cc: | "Pgsql-Hackers" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Dirty Buffer Writing [was Proposed LogWriter Scheme] |
Date: | 2002-10-08 02:45:31 |
Message-ID: | DMEEJMCDOJAKPPFACMPMEEFMCEAA.curtis@galtair.com |
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Thread: | |
Lists: | pgsql-hackers |
> Greg Copeland <greg(at)CopelandConsulting(dot)Net> writes:
> > Doesn't this also increase the likelihood that people will be
> > running in a buffer-poor environment more frequently that I
> > previously asserted, especially in very heavily I/O bound
> > systems? Unless I'm mistaken, that opens the door for a
> > general case of why an aio implementation should be looked into.
Neil Conway replies:
> Well, at least for *this specific sitation*, it doesn't really change
> anything -- since FreeBSD doesn't implement POSIX AIO as far as I
> know, we can't use that as an alternative.
I haven't tried it yet but there does seem to be an aio implementation that
conforms to POSIX in FreeBSD 4.6.2. Its part of the kernel and can be
found in:
/usr/src/sys/kern/vfs_aio.c
> However, I'd suspect that the FreeBSD kernel allows for some way to
> tune the behavior of the syncer. If that's the case, we could do some
> research into what settings are more appropriate for FreeBSD, and
> recommend those in the docs. I don't run FreeBSD, however -- would
> someone like to volunteer to take a look at this?
I didn't see anything obvious in the docs but I still believe there's some
way to tune it. I'll let everyone know if I find some better settings.
> BTW Curtis, did you happen to check whether this behavior has been
> changed in FreeBSD 5.0?
I haven't checked but I will.
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