From: | Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com> |
---|---|
To: | Wayne Beaver <wayne(at)acedsl(dot)com> |
Cc: | pgsql-performance(at)postgresql(dot)org |
Subject: | Re: Manual vacs 5x faster than autovacs? |
Date: | 2009-11-12 16:38:48 |
Message-ID: | dcc563d10911120838q56b50afxadabd7e59cbbb976@mail.gmail.com |
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Lists: | pgsql-performance |
On Thu, Nov 12, 2009 at 9:33 AM, Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com> wrote:
> On Thu, Nov 12, 2009 at 9:14 AM, Wayne Beaver <wayne(at)acedsl(dot)com> wrote:
>> Hmm, looks like I've been myth-busted here.
>>
>> $ top | grep -E '29343|31924|29840|PID'; echo
>> PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
>> 29840 postgres 15 0 2150m 203m 194m S 0 2.5 0:00.59 postmaster
>> 29343 postgres 15 0 2137m 360m 356m S 1 4.5 0:00.92 postmaster
>> 31924 postgres 15 0 2135m 73m 70m S 1 0.9 0:00.44 postmaster
>>
>> So my claims of resource-usage appear incorrect.
>>
>> I'd seen autovacs running for hours and had mis-attributed this to growing
>> query times on those tables - my thought was that "shrinking" the tables
>> "more quickly" could make them "more-optimized", more often. Sounds like I
>> could be chasing the wrong symptoms, though.
>
> Now it is quite possible that a slow autovac is causing your queries
> to run slower. And it's that autovac isn't keeping up. One of the
> verious serious shortcomings of autovac in 8.1 (or was it 8.0? I
> think it was 8.1 as well) was that it only had one worker thread. So,
> if it has a moderate to high cost delay, then it might be able to keep
> up with the job and your tables will become bloated.
might NOT be able to keep up
>
> The problem isn't that autovac is stealing too many resources, it's
> that it's not stealing enough.
>
> The first quick fix is 8.3 which has more efficient vacuuming code and
Whoops I see you're technically running 8.3, but you're running RC2
for some reason? I don't usually run 8.x.0 in production. Let alone
RCs. You should really update before some nasty bug that's been
squashed in later releases bites you.
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