From: | Kevin Grittner <kgrittn(at)gmail(dot)com> |
---|---|
To: | Andres Freund <andres(at)anarazel(dot)de> |
Cc: | Kevin Grittner <kgrittn(at)postgresql(dot)org>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, "pgsql-committers(at)postgresql(dot)org" <pgsql-committers(at)postgresql(dot)org> |
Subject: | Re: [HACKERS] Re: pgsql: Avoid extra locks in GetSnapshotData if old_snapshot_threshold < |
Date: | 2016-04-12 20:14:07 |
Message-ID: | CACjxUsOwA7+6xU85zmaVP8QYUQjo1tBiotSJ6W-hOSr=qHz50A@mail.gmail.com |
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On Tue, Apr 12, 2016 at 2:53 PM, Kevin Grittner <kgrittn(at)gmail(dot)com> wrote:
> Readonly with client and job counts matching scale.
Single-socket i7, BTW.
>> A lot of this will be different between
>> single-socket and multi-socket servers; as soon as you have the latter
>> the likelihood of contention being bad goes up dramatically.
>
> Yeah, I know, and 4 socket has been at least an order of magnitude
> more problematic in my experience than 2 socket. And the problems
> are far, far, far worse on kernels prior to 3.8, especially on 3.x
> before 3.8, so it's hard to know how to take any report of problems
> on a 4 node NUMA machine without knowing the kernel version.
Also, with 4 node NUMA I have seen far better scaling with
hyper-threading turned off. I know there are environments where it
helps, but high-concurrency on multi-node NUMA is not one of them.
So, anyway, mentioning the HT setting is important, too.
Kevin Grittner
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