On Tue, Nov 16, 2010 at 8:22 PM, Tom Lane <tgl@xxxxxxxxxxxxx> wrote: > Josh Berkus <josh@xxxxxxxxxxxx> writes: >>> Well, we're not going to increase the default to gigabytes, but we could >>> very probably increase it by a factor of 10 or so without anyone >>> squawking. It's been awhile since I heard of anyone trying to run PG in >>> 4MB shmmax. How much would a change of that size help? > >> Last I checked, though, this comes out of the allocation available to >> shared_buffers. And there definitely are several OSes (several linuxes, >> OSX) still limited to 32MB by default. > > Sure, but the current default is a measly 64kB. We could increase that > 10x for a relatively small percentage hit in the size of shared_buffers, > if you suppose that there's 32MB available. The current default is set > to still work if you've got only a couple of MB in SHMMAX. > > What we'd want is for initdb to adjust the setting as part of its > probing to see what SHMMAX is set to. > > regards, tom lane > > In all the performance tests that I have done, generally I get a good bang for the buck with wal_buffers set to 512kB in low memory cases and mostly I set it to 1MB which is probably enough for most of the cases even with high memory. That 1/2 MB wont make drastic change on shared_buffers anyway (except for edge cases) but will relieve the stress quite a bit on wal buffers. Regards, Jignesh -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
