On Sun, Jun 11, 2006 at 07:43:03PM -0400, Tom Lane wrote: > > On Sun, 11 Jun 2006, Kris Kennaway wrote: > >> Why does postgresql change its process title so frequently and how can > >> this be disabled? Profiling suggests it's a fairly serious > >> performance bottleneck. > > Let's see the evidence.
The calls to setproctitle() (it looks like 4 setproctitle syscalls per DB query) are causing contention on the Giant lock 25% of the time on a dual p4 + HTT. Disabling process title setting completely gives an 8% peak performance boost to the super-smack select benchmark. It's actually worse than that in stock FreeBSD because in certain "mixed" workloads with other sources of Giant contention present they will contend with each other to make overall machine performance much worse; that's the "serious" aspect, although 8% performance loss just in case someone should ever want to run 'ps' to check the state of the database processes is nothing to laugh at either. Kris
pgpyrvGOB2EdD.pgp
Description: PGP signature
