Re: 7.1 vs. 7.2 on AIX 5L

From: "Zeugswetter Andreas SB SD" <ZeugswetterA(at)spardat(dot)at>
To: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "Tatsuo Ishii" <t-ishii(at)sra(dot)co(dot)jp>
Cc: <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: 7.1 vs. 7.2 on AIX 5L
Date: 2002-01-15 09:44:55
Message-ID: 46C15C39FEB2C44BA555E356FBCD6FA41EB4AE@m0114.s-mxs.net
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Tom wrote:
> > [ compare_and_swap man page ]
>
> Looks kinda baroque. What about the referenced fetch_and_or routine?
> If that's atomic it might be closer to TAS semantics.

Thanks for the hint!
Tatsuo, can you try the performance of fetch_and_or on your machine ?
Replace the cs() line in s_lock.h with the following:

<-- #define TAS(lock) cs((int *) (lock), 0, 1)
--> #define TAS(lock) fetch_and_or(lock, 1)

On my machine the various implemtations have the following runtimes:
(with a modified s_lock test that does not sleep, and SPINS_PER_DELAY 100000)

with LinuxPPC asm: 1m5.16s (Which may not work relyably on SMP)
with cs: 1m12.25s
with fetch_and_or: 1m26.71s

I don't know if that is enough difference to worry about.

Andreas

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