| From: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
|---|---|
| To: | Aleksander Alekseev <a(dot)alekseev(at)postgrespro(dot)ru> |
| Cc: | Andres Freund <andres(at)anarazel(dot)de>, Robert Haas <robertmhaas(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Patch: fix lock contention for HASHHDR.mutex |
| Date: | 2015-12-18 08:49:23 |
| Message-ID: | CAA4eK1KOnADjGV2D0EiW2jUowp7uQp3MQmrR4wQY+P6it5m8ow@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, Dec 17, 2015 at 9:33 PM, Aleksander Alekseev <
a(dot)alekseev(at)postgrespro(dot)ru> wrote:
>
> > It'd really like to see it being replaced by a queuing lock
> > (i.e. lwlock) before we go there. And then maybe partition the
> > freelist, and make nentries an atomic.
>
> I believe I just implemented something like this (see attachment). The
> idea is to partition PROCLOCK hash table manually into NUM_LOCK_
> PARTITIONS smaller and non-partitioned hash tables. Since these tables
> are non-partitioned spinlock is not used and there is no lock
> contention.
>
This idea can improve the situation with ProcLock hash table, but I
think IIUC what Andres is suggesting would reduce the contention
around dynahash freelist and can be helpful in many more situations
including BufMapping locks.
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com
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