On 2017-06-05 16:22, Sokolov Yura wrote:
> Good day, everyone.
>
> This patch improves performance of contended LWLock.
> Patch makes lock acquiring in single CAS loop:
> 1. LWLock->state is read, and ability for lock acquiring is detected.
> If there is possibility to take a lock, CAS tried.
> If CAS were successful, lock is aquired (same to original version).
> 2. but if lock is currently held by other backend, we check ability for
> taking WaitList lock. If wait list lock is not help by anyone, CAS
> perfomed for taking WaitList lock and set LW_FLAG_HAS_WAITERS at
> once.
> If CAS were successful, then LWLock were still held at the moment
> wait
> list lock were held - this proves correctness of new algorithm. And
> Proc is queued to wait list then.
> 3. Otherwise spin_delay is performed, and loop returns to step 1.
>
I'm sending rebased version with couple of one-line tweaks.
(less skip_wait_list on shared lock, and don't update spin-stat on
aquiring)
With regards,
--
Sokolov Yura aka funny_falcon
Postgres Professional: https://postgrespro.ru
The Russian Postgres Company
--
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers