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Re: User concurrency thresholding: where do I look?

From: "Simon Riggs" <simon(at)2ndquadrant(dot)com>
To: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: "Jignesh K(dot) Shah" <J(dot)K(dot)Shah(at)Sun(dot)COM>,"Josh Berkus" <josh(at)agliodbs(dot)com>,<pgsql-performance(at)postgresql(dot)org>,"Alvaro Herrera" <alvherre(at)commandprompt(dot)com>
Subject: Re: User concurrency thresholding: where do I look?
Date: 2007-07-23 17:50:53
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
On Mon, 2007-07-23 at 12:35 -0400, Tom Lane wrote:
> "Simon Riggs" <simon(at)2ndquadrant(dot)com> writes:
> > Well, I discover there is an allocation of 8232 (inflation...) made once
> > per statement by a memory context called... ExecutorState. Still not
> > sure exactly which allocation this is, but its definitely once per
> > statement on pgbench, which should narrow it down. Plan, query etc?
> Are you working with stock sources?  The only allocation exceeding 1K
> that I can see during pgbench is BTScanOpaqueData, which is 6600 bytes.
> (Checked by setting a conditional breakpoint on AllocSetAlloc.)  The
> path that allocates a single-chunk block is never taken at all.

I do have the bitmap patch currently applied, but it doesn't touch that
part of the code.

(gdb) p size
$1 = 8232

(gdb) p sizeof(int)
$2 = 4

(gdb) p sizeof(BTScanPosData)
$3 = 4104

Since my notes say I got 8228 last year, seems reasonable.

  Simon Riggs

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