From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
---|---|
To: | Jan Wieck <JanWieck(at)Yahoo(dot)com> |
Cc: | Manfred Spraul <manfred(at)colorfullife(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org, markw(at)osdl(dot)org |
Subject: | Re: [PATCHES] update i386 spinlock for hyperthreading |
Date: | 2003-12-30 16:48:10 |
Message-ID: | 200312301648.hBUGmAT01243@candle.pha.pa.us |
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Lists: | pgsql-general pgsql-hackers pgsql-patches |
Jan Wieck wrote:
> Manfred Spraul wrote:
> > Bruce Momjian wrote:
> >
> >>>Anyone see an attack path here?
> >>>
> >>>
> >>
> >>Should we have one lock per hash bucket rather than one for the entire
> >>hash?
> >>
> >>
> > That's the simple part. The problem is the aging strategy: we need a
> > strategy that doesn't rely on a global list that's updated after every
> > lookup. If I understand the ARC code correctly, there is a
> > STRAT_MRU_INSERT(cdb, STRAT_LIST_T2) that happen in every lookup.
>
> Moving the Cache Directory Block (cdb) on a hit to the MRU position of
> the appropriate queue "is the bookkeeping" of this strategy. The whole
> algorithm is based on it, and I don't see yet how to avoid that without
> opening a huge can of worms that look like deadlocks. But I'll think
> about it for a while.
If we can't eliminate the global lock, and we reduce its duration?
--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073
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