Re: [PATCHES] update i386 spinlock for hyperthreading

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Manfred Spraul <manfred(at)colorfullife(dot)com>
Cc: Jan Wieck <JanWieck(at)Yahoo(dot)com>, Bruce Momjian <pgman(at)candle(dot)pha(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 17:16:15
Message-ID: 23806.1072804575@sss.pgh.pa.us
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Manfred Spraul <manfred(at)colorfullife(dot)com> writes:
> Are there strategies that do not rely on a global lock? The Linux kernel
> uses a lazy LRU with referenced bits: on access, the referenced bit is
> set. The freespace logic takes pages from the end of a linked list, and
> checks that bit: if it's set, then the page is moved back to the top of
> the list. Otherwise it's a candidate for replacement.

I think this is the same idea as what I was just suggesting: add an
extra check when looking for a free page, and thereby avoid having to
lock/update the global datastructure during ReadBuffer.

regards, tom lane

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