| From: | Merlin Moncure <mmoncure(at)gmail(dot)com> |
|---|---|
| To: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com> |
| Cc: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Better LWLocks with compare-and-swap (9.4) |
| Date: | 2013-05-13 14:21:27 |
| Message-ID: | CAHyXU0x+oYbf1=wYX_=DdsgmmDdQ9yQTm2A469DZRJqs1u-BvQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Mon, May 13, 2013 at 7:50 AM, Heikki Linnakangas
<hlinnakangas(at)vmware(dot)com> wrote:
> The attached patch is still work-in-progress. There needs to be a configure
> test and fallback to spinlock if a CAS instruction is not available. I used
> the gcc __sync_val_compare_and_swap() builtin directly, that needs to be
> abstracted. Also, in the case that the wait queue needs to be manipulated,
> the code spins on the CAS instruction, but there is no delay mechanism like
> there is on a regular spinlock; that needs to be added in somehow.
These are really interesting results. Why is the CAS method so much
faster then TAS? Did you see any contention?
merlin
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