From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Tatsuo Ishii <t-ishii(at)sra(dot)co(dot)jp>, pgsql-hackers(at)postgresql(dot)org, jwbaker(at)acm(dot)org |
Subject: | Re: LWLock contention: I think I understand the problem |
Date: | 2002-01-03 17:08:34 |
Message-ID: | 200201031708.g03H8Ya15393@candle.pha.pa.us |
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Lists: | pgsql-hackers pgsql-odbc |
Tom Lane wrote:
> Tatsuo Ishii <t-ishii(at)sra(dot)co(dot)jp> writes:
> > Ok, here is a pgbench (-s 10) result on an AIX 5L box (4 way).
> > "7.2 with patch" is for the previous patch. "7.2 with patch (revised)"
> > is for the this patch. I see virtually no improvement.
>
> If anything, the revised patch seems to make things slightly worse :-(.
> That agrees with my measurement on a single CPU.
>
> I am inclined to use the revised patch anyway, though, because I think
> it will be less prone to starvation (ie, a process repeatedly being
> awoken but failing to get the lock). The original form of lwlock.c
> guaranteed that a writer could not be locked out by large numbers of
> readers, but I had to abandon that goal in the first version of the
> patch. The second version still doesn't keep the writer from being
> blocked by active readers, but it does ensure that readers queued up
> behind the writer won't be released. Comments?
Yes, I agree with the later patch.
>
> > Please note that xy axis are now in log scale.
>
> Seems much easier to read this way. Thanks.
Yes, good idea. I want to read up on gnuplot. I knew how to use it long
ago.
--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
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