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Re: [BUGS] BUG #2401: spinlocks not available on amd64

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Theo Schlossnagle <jesus(at)omniti(dot)com>
Cc: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>, josh(dot)berkus(at)sun(dot)com, robert(dot)lor(at)sun(dot)com, PostgreSQL-patches <pgsql-patches(at)postgresql(dot)org>
Subject: Re: [BUGS] BUG #2401: spinlocks not available on amd64
Date: 2006-04-29 19:34:28
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-bugspgsql-patches
Theo Schlossnagle <jesus(at)omniti(dot)com> writes:
> I'd remind everyone that the spinlock stuff is entirely optional at 
> build time.

Not really.  The performance hit for not having hardware spinlocks is
so severe that it's not considered a reasonable fallback.

> I also think it immensely useful to replace all of the tas subsystem 
> with cas so that one could reliabily lock these atomics with the process 
> id of the locker.

I cannot, ever once in my years working on Postgres, remember having
wanted such a thing.  I am strongly against mucking with the spinlock
code for mere aesthetics --- it's too fragile and hard to test,
especially on platforms you don't have ready access to.

In short, it ain't broken and we don't need to fix it.

			regards, tom lane

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