Date: Wed, 10 Jul 2002 14:15:09 -0400 From: Vivek Khera <khera@kcilink.com> To: stable@freebsd.org, pgsql-general@postgresql.org Subject: was there a change in FreeBSD SHM implementation from 4.4 to 4.6? (postgres trouble) Message-ID: <15660.31149.224797.969563@onceler.kciLink.com>
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I have a dual cpu box with 2GB RAM dedicated to running Postgres. Last week, I upgraded FreeBSD from 4.4-STABLE to 4.6-RELEASE-p1. When I went to restart postgres, it complained that it could not allocate the shared memory segment. I'm running Postgres 7.2.1. For those familiar with postgres, I was using shared_buffers=100000 with 4.4, but had to back that down to 32000 for 4.6. This is obviously impacting performance... The kern.ipc.* settings have not changed. In my /etc/sysctl.conf file, I set kern.ipc.shmmax=268435456 kern.ipc.shmall=65535 kern.ipc.shm_use_phys=1 With FreeBSD 4.6, I even upped the shmmax to 1073741824 to no avail. I also set this in the kernel (so as to eliminate any issues with setting it at boot time). However, it does produce a most peculiar error message when running postgres: -- cut here -- IpcMemoryCreate: shmget(key=5432001, size=665346048, 03600) failed: Cannot allocate memory This error usually means that PostgreSQL's request for a shared memory segment exceeded available memory or swap space. To reduce the request size (currently 665346048 bytes), reduce PostgreSQL's shared_buffers parameter (currently 80000) and/or its max_connections parameter (currently 48). -- cut here -- Now, by my arithmetic, 665346048 is certainly less than 1073741824 by quite a bit. I did not recompile postgres after the FreeBSD upgrade. Has something changed from 4.4-STABLE that would cause such a failure? The funny thing is that it worked just fine with FBSD 4.4 and the lower setting of shmmax (even with 100000 shared_buffers), so something is making postgres try to allocate a larger hunk of memory. I just don't know what. Any advice would be appreciated. -- =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Vivek Khera, Ph.D. Khera Communications, Inc. Internet: khera@kciLink.com Rockville, MD +1-240-453-8497 AIM: vivekkhera Y!: vivek_khera http://www.khera.org/~vivek/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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