On Mar 26, 2010, at 5:25 PM, Scott Carey wrote: > Linux until recently does not account for shared memory properly in its swap > 'aggressiveness' decisions. > Setting shared_buffers larger than 35% is asking for trouble. > > You could try adjusting the 'swappiness' setting on the fly and seeing how it > reacts, but one consequence of that is trading off disk swapping for kswapd > using up tons of CPU causing other trouble. Thanks for the tip. I believe we've tried tuning the 'swappiness' setting on the fly, but it had no effect. We're hypothesizing that perhaps 'swappiness' only comes into effect at the beginning of a process, so we would have to restart the daemon to actually make it go into effect--would you know about this?
> Either use one of the last few kernel versions (I forget which addressed the > memory accounting issues, and haven't tried it myself), or turn > shared_buffers down. I recommend trying 10GB or so to start. We're currently using CentOS 2.6.18-164.6.1.el5 with all the default settings. If this is after the one that dealt with memory accounting issues, I agree that I'll likely have to lower my shared_buffers. My sysctl.conf shows the following: > kernel.msgmnb = 65536 > kernel.msgmax = 65536 > kernel.shmmax = 68719476736 > kernel.shmall = 4294967296 BTW, I forgot to mention that I'm using FusionIO drives for my data storage, but I'm pretty sure this is not relevant to the issue I'm having. Thanks for the help! --Richard -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
