| 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 |
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| 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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