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Re: Re: significant performance hit whenever autovacuum runs after upgrading from 9.0 -> 9.1

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Lonni J Friedman <netllama@xxxxxxxxx> writes:
> After banging my head on the wall for  a long time, I happened to
> notice that khugepaged was consuming 100% CPU every time autovacuum
> was running.  I did:
> echo "madvise" > /sys/kernel/mm/transparent_hugepage/defrag
> and immediately the entire problem went away.

Fascinating.

> So this looks like a nasty Fedora16 kernel bug to me, or maybe
> postgresql & Fedora16's default kernel settings are just not
> compatible?

I agree, kernel bug.  What kernel version are you using exactly?

> Is anyone else using Fedora16 & PostgreSQL-9.1 ?

I use an F16 box daily, but can't claim to have done major performance
testing with it.  Can you put together a summary of your nondefault
Postgres settings?  I wonder whether it only kicks in for a certain
size of shared memory for instance.

			regards, tom lane

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