On Dec 5, 2007, at 7:50 AM, Robert Treat wrote:
On Wednesday 05 December 2007 07:22, Alvaro Herrera wrote:
Robert Treat wrote:
On Monday 03 December 2007 20:22, Erik Jones wrote:
Interesting. If this is anything you'd like to look into I can
provide whatever diagnostic output you need (iostat, vmstat, dtrace
script outputs, etc...) but I do have to reiterate that we are an
extreme corner case due to out schema size. For now, is
renaming the
#define'd paths for the stats file and temp file sufficient for
moving them? Basically, we'd like to move them onto a RAM disk to
give our disks a break.
Yeah, we've noticed the same problem (pgstat is the most active
file on
the system... uncovered in much the same way... go solaris).
Actually I
was wondering if it could be done with symlinks, a la moving xlogs.
Not really, because a new file is created and renamed in place
each time
it's going to be rewritten. So the symlink would be lost in the
first
file rewrite.
Ah yeah, thats what I concluded back then.
The first idea that comes to mind is to make the path configurable
via
GUC, so the user could set it to be written to an in-memory
filesystem
(/tmp in Solaris?).
Yep, thought of that to, though it was after feature freeze so I
didn't
propose it. Course if someone wants to sneak that in it would be
cool :-)
But then I thought, why do we need it to be a file
at all? Why not use a mmap'ed memory area or something like that,
and
only write it to a file on postmaster shutdown? (Losing the file on
unclean shutdown is not a problem, because the file is removed
anyway.)
I suppose you need some facility to spill to disk, so maybe being
in a file is
better? Seems it might not be in most cases... I wonder how big a
memory
space we (or Erik) need.
We made the swapfs 300MB which is actually way more than we need as I
don't think I've seen our pgstat.stat file crack 10MB using the
entirely scientific method of spot-checking :)
Erik Jones
Software Developer | Emma®
erik@xxxxxxxxxx
800.595.4401 or 615.292.5888
615.292.0777 (fax)
Emma helps organizations everywhere communicate & market in style.
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