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Re: RC2 and open issues

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Richard Huxton <dev(at)archonet(dot)com>
Cc: simon(at)2ndquadrant(dot)com, Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>,PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: RC2 and open issues
Date: 2004-12-21 15:26:48
Message-ID: 7942.1103642808@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Richard Huxton <dev(at)archonet(dot)com> writes:
> However, one thing you can say is that if block B hasn't been written to 
> since you last checked, then any blocks older than that haven't been 
> written to either.

[ itch... ]  Can you?  I don't recall exactly when a block gets pushed
up the ARC list during a ReadBuffer/WriteBuffer cycle, but at the very
least I'd have to say that this assumption is vulnerable to race
conditions.

Also, the cntxDirty mechanism allows a block to be dirtied without
changing the ARC state at all.  I am not very clear on whether Vadim
added that mechanism just for performance or because there were
fundamental deadlock issues without it; but in either case we'd have
to think long and hard about taking it out for the bgwriter's benefit.

			regards, tom lane

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Subject: Re: Bgwriter behavior
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Subject: Bgwriter behavior

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