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Re: Odd blocking (or massively latent) issue - even with EXPLAIN

From:	"Martin French" <Martin(dot)French(at)romaxtech(dot)com>
To:	Jim Vanns <james(dot)vanns(at)framestore(dot)com>
Cc:	pgsql-performance(at)postgresql(dot)org,pgsql-performance-owner(at)postgresql(dot)org
Subject:	Re: Odd blocking (or massively latent) issue - even with EXPLAIN
Date:	2012-07-24 09:18:53
Message-ID:	OFD096C18F.C98A054A-ON80257A45.0032E783-80257A45.00332C2A@LocalDomain
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<html><body><tt>Hi Jim,</tt> <tt>> > I've already tried something very similar using dd. No performance > penalties during a normal running of the system - or when this blocking > happens either actually. But I agree, it does indeed sound like some > sort of I/O problem. I just don't know what! I do have a few more tricks > up my sleeve that I'll try today. I'll post any results that I have. </tt> <tt>Ok, let me know how you get on. </tt> <tt>> > That latter test - won't that pretty much just read from the page cache? > 'sync' may well have forced dirty pages to disk but does it actually > evict them to? </tt> <tt>Basically, the cache is avoided because of the size of the file. 6000000 blocks at 8k exceeds the size of RAM in the machine, so it *should* miss the cache and hit the disk directly. :)</tt> <tt>> > Anyway, that is off topic... perhaps ;) > > Thanks again, > > Jim > </tt> <tt>Cheers</tt> <tt>Martin </tt>=============================================

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In response to

Re: Odd blocking (or massively latent) issue - even with EXPLAIN at 2012-07-24 08:48:11 from Jim Vanns

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Re: Odd blocking (or massively latent) issue - even with EXPLAIN at 2012-07-24 09:34:11 from Jim Vanns
Re: Odd blocking (or massively latent) issue - even with EXPLAIN at 2012-08-16 16:14:36 from Jim Vanns

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