Re: Wait free LW_SHARED acquisition - v0.9
От | Amit Kapila |
---|---|
Тема | Re: Wait free LW_SHARED acquisition - v0.9 |
Дата | |
Msg-id | CAA4eK1JiP-yCyNXwLTxA29ErkWC=VNBk4zjF2BZuLkKEaheoew@mail.gmail.com обсуждение исходный текст |
Ответ на | Re: Wait free LW_SHARED acquisition - v0.9 (Merlin Moncure <mmoncure@gmail.com>) |
Список | pgsql-hackers |
On Wed, Oct 15, 2014 at 12:06 AM, Merlin Moncure <mmoncure@gmail.com> wrote:
>
> A while back, I submitted a minor tweak to the clock sweep so that,
> instead of spinlocking every single buffer header as it swept it just
> did a single TAS as a kind of a trylock and punted to the next buffer
> if the test failed on the principle there's not good reason to hang
> around. You only spin if you passed the first test; that should
> reduce the likelihood of actual spinning to approximately zero. I
> still maintain there's no reason not to do that (I couldn't show a
> benefit but that was because mapping list locking was masking any
> clock sweep contention at that time).
If you feel that can now show the benefit, then I think you can rebase
>
> A while back, I submitted a minor tweak to the clock sweep so that,
> instead of spinlocking every single buffer header as it swept it just
> did a single TAS as a kind of a trylock and punted to the next buffer
> if the test failed on the principle there's not good reason to hang
> around. You only spin if you passed the first test; that should
> reduce the likelihood of actual spinning to approximately zero. I
> still maintain there's no reason not to do that (I couldn't show a
> benefit but that was because mapping list locking was masking any
> clock sweep contention at that time).
If you feel that can now show the benefit, then I think you can rebase
it for the coming commit fest (which is going to start today).
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