From: | Andres Freund <andres(at)2ndquadrant(dot)com> |
---|---|
To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Scaling shared buffer eviction |
Date: | 2014-10-02 15:20:55 |
Message-ID: | 20141002152055.GC25554@awork2.anarazel.de |
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Thread: | |
Lists: | pgsql-hackers |
On 2014-10-02 10:56:05 -0400, Robert Haas wrote:
> On Thu, Oct 2, 2014 at 10:44 AM, Andres Freund <andres(at)2ndquadrant(dot)com> wrote:
> > On 2014-10-02 10:40:30 -0400, Robert Haas wrote:
> >> On Thu, Oct 2, 2014 at 10:36 AM, Andres Freund <andres(at)2ndquadrant(dot)com> wrote:
> >> >> OK.
> >> >
> >> > Given that the results look good, do you plan to push this?
> >>
> >> By "this", you mean the increase in the number of buffer mapping
> >> partitions to 128, and a corresponding increase in MAX_SIMUL_LWLOCKS?
> >
> > Yes. Now that I think about it I wonder if we shouldn't define MAX_SIMUL_LWLOCKS like
> > #define MAX_SIMUL_LWLOCKS (NUM_BUFFER_PARTITIONS + 64)
> > or something like that?
>
> Nah. That assumes NUM_BUFFER_PARTITIONS will always be the biggest
> thing, and I don't see any reason to assume that, even if we're making
> it true for now.
The reason I'm suggesting is that NUM_BUFFER_PARTITIONS (and
NUM_LOCK_PARTITIONS) are the cases where we can expect many lwlocks to
be held at the same time. It doesn't seem friendly to users
experimenting with changing this to know about a define that's private
to lwlock.c.
But I'm fine with doing this not at all or separately - there's no need
to actually do it together.
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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