On 6/1/05, Mark Kirkwood <[EMAIL PROTECTED]> wrote: > Cosimo Streppone wrote: > > ######### Config ############ > >> /etc/sysctl.conf: > >> kernel.shmall = 786432000 > >> kernel.shmmax = 786432000 > > > > I think you have a problem here. > > kernel.shmmax should *not* be set to an amount of RAM, but > > to maximum number of shared memory pages, which on a typical linux system > > is 4kb. Google around: > > > This is somewhat confusing : > > kernel.shmmax is in bytes (max single segment size) > kernel.shmall is in (4k) pages (max system wide allocated segment pages)
Can someone resummarize the situation with these linux parameters for the dummies? I thought I had my calculations all sorted out but now I've confused myself again. The documentation at http://www.postgresql.org/docs/8.0/interactive/kernel-resources.html puts the same figure into both values but the posts here seem to suggest that is wrong? Or is it different on a 2.4 kernel and the documentation needs updating? In my specific case I have about 800meg of memory on a linux 2.4 kernel box. Based on the powerpostgresql.com Performance Checklist [1] and Annotated Postgresql.conf [2] I understand that: -I should have less than 1/3 of my total memory as shared_buffers -For my server 15000 is a fairly reasonable starting point for shared_buffers which is ~120MB -I have 100 max_connections. So I was going to set SHMMAX to 134217728 (ie 128 Meg) What should SHMALL be? The current system values are [EMAIL PROTECTED]:~/data$ cat /proc/sys/kernel/shmmax 33554432 [EMAIL PROTECTED]:~/data$ cat /proc/sys/kernel/shmall 2097152 ie SHMALL seems to be 1/16 of SHMMAX Paul [1] http://www.powerpostgresql.com/PerfList/ [2] http://www.powerpostgresql.com/Downloads/annotated_conf_80.html ---------------------------(end of broadcast)--------------------------- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
