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Re: Experimental patch for inter-page delay in VACUUM

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Stephen" <jleelim(at)xxxxxx(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Experimental patch for inter-page delay in VACUUM
Date: 2003-11-01 19:12:49
Message-ID: 2254.1067713969@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
"Stephen" <jleelim(at)xxxxxx(dot)com> writes:
> also as there are less processes waiting to complete. I find a value of 1ms
> to 5ms is quite good and will keep system responsive. Going from 10ms to 1ms
> didn't seem to reduce the total vacuum time by much and I'm not sure why.

On most Unixen, the effective resolution of sleep requests is whatever
the scheduler time quantum is --- and 10ms is the standard quantum in
most cases.  So any delay less than 10ms is going to be interpreted as
10ms.

I think on recent Linuxen it's possible to adjust the time quantum, but
whether this would be a net win isn't clear; presumably a shorter
quantum would result in more scheduler overhead and more process-swap
penalties.

			regards, tom lane

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