Re: buffer assertion tripping under repeat pgbench load

From: Greg Stark <stark(at)mit(dot)edu>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Greg Smith <greg(at)2ndquadrant(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Andres Freund <andres(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: buffer assertion tripping under repeat pgbench load
Date: 2012-12-26 22:40:09
Message-ID: CAM-w4HNorMJvefyUMBhFQ22QD8KXpr7h9xzgD2RToFKJr8NB_g@mail.gmail.com
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On Wed, Dec 26, 2012 at 6:33 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Yeah, that destroys my theory that there's something broken about index
> management specifically. Now we're looking for something that can
> affect any buffer's refcount, which more than likely means it has
> nothing to do with the buffer's contents ...

Also, do you have the buffer id of the broken buffer? I wonder if it's
not just any buffer but always the same same buffer even if it's a
different block in that buffer. e.g. maybe it's always the first
buffer because something is overwriting past the end of the
BufferBlocks array which is declared immediately before
PrivateRefCount. (Or maybe your compiler is laying out these objects
in a different way from most people's compilers and we're overwriting
past the end of some other object routinely but yours is the only
place where it's being laid out preceding a critical data structure)

--
greg

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