| From: | "Michael Paesold" <mpaesold(at)gmx(dot)at> |
|---|---|
| To: | "Marko Kreen" <marko(at)l-t(dot)ee>, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Spinlocks, yet again: analysis and proposed patches |
| Date: | 2005-09-14 20:56:22 |
| Message-ID: | 002c01c5b96e$c3c95560$0f01a8c0@zaphod |
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| Lists: | pgsql-hackers |
Tom Lane wrote:
>I wrote:
>> We could ameliorate this if there were a way to acquire ownership of the
>> cache line without necessarily winning the spinlock. I'm imagining
>> that we insert a "dummy" locked instruction just ahead of the xchgb,
>> which touches the spinlock in such a way as to not change its state.
>
> I tried this, using this tas code:
...
I have tried it on the P4 w/ HT.
CVS tip 1: 37s 2: 78s 4: 159s 8: 324
only slock-no-cmpb 1: 37s 2: 82s 4: 178s 8: 362
only dummy-locking 1: 44s 2: 96s 4: 197s ...
I guess there is no reason to try any more.
Best Regards,
Michael Paesold
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