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Subject: Re: User concurrency thresholding: where do I look?
From: "Simon Riggs" <simon@2ndquadrant.com>
To: "Jignesh K. Shah" <J.K.Shah@Sun.COM>
Cc: "Tom Lane" <tgl@sss.pgh.pa.us>, "Josh Berkus" <josh@agliodbs.com>,
	<pgsql-performance@postgresql.org>,
	"Alvaro Herrera" <alvherre@commandprompt.com>
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On Thu, 2007-07-26 at 15:44 -0400, Jignesh K. Shah wrote:
> BEAUTIFUL!!!
> 
> Using the Patch I can now go upto 1300 users without dropping.. But now 
> it still repeats at 1300-1350 users..

OK, can you try again with 16 and 32 buffers please?  We need to know
how many is enough and whether this number needs to be variable via a
parameter, or just slightly larger by default. Thanks.

> I corrected the Lock Descriptions based on what I got from lwlock.h and 
> retried the whole scalability again with profiling again.. This time it 
> looks like the ProcArrayLock

That's what I would expect with that many users.

>              Lock Id            Mode           Count
>           XidGenLock       Exclusive               1
>      CLogControlLock          Shared               2
>           XidGenLock          Shared               2
>         WALWriteLock       Exclusive               4
>        WALInsertLock       Exclusive               8
>      CLogControlLock       Exclusive               9
>        ProcArrayLock       Exclusive               9

...but as Tom mentioned, we need to do longer runs now so these counts
get to somewhere in the hundreds so we have some statistical validity.

-- 
  Simon Riggs
  EnterpriseDB  http://www.enterprisedb.com