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Re: Admission Control

From: Mark Kirkwood <mark(dot)kirkwood(at)catalyst(dot)net(dot)nz>
To: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Admission Control
Date: 2010-06-30 23:26:50
Message-ID: 4C2BD2BA.3020504@catalyst.net.nz (view raw or flat)
Thread:
Lists: pgsql-hackers
On 29/06/10 05:36, Josh Berkus wrote:
>
> Having tinkered with it, I'll tell you that (2) is actually a very 
> hard problem, so any solution we implement should delay as long as 
> possible in implementing (2).  In the case of Greenplum, what Mark did 
> originally IIRC was to check against the global memory pool for each 
> work_mem allocation.  This often resulted in 100's of global locking 
> checks per query ... like I said, feasible for DW, not for OLTP.

Actually only 1 lock check per query, but certainly extra processing and 
data structures to maintain the pool information... so, yes certainly 
much more suitable for DW (AFAIK we never attempted to measure the 
additional overhead for non DW workload).

Cheers

Mark

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