Date: Wed, 10 Dec 2008 17:36:17 +0100 From: "Hell, Robert" <Robert.Hell@fabasoft.com> To: <freebsd-questions@freebsd.org> Subject: PostgreSQL on FreeBSD 7.0 amd64 with more than 2GB shared memory Message-ID: <B710F3299F04664DB6B37C258FDEEB940229B958@FABAMAIL.fabagl.fabasoft.com>
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Hi,
I'm trying to run PostgreSQL 8.3 on a FreeBSD 7.0 amd64 server with more
than 2GB shared memory. The machine has 32GB RAM installed.
After setting kern.ipc.shmmax and kern.ipc.shmall to the appropriate
values, I still had no chance to start postgres with more than 2GB of
shared memory.
I wrote a small test which does the same as postgres: shmget and shmat:
#include <sys/ipc.h>
#include <sys/shm.h>
#include <stdio.h>
#include <errno.h>
int main()
{
int shmid, memKey =3D 1;
void *memAddress;
unsigned long size =3D 2147483648UL;
shmid =3D shmget(memKey, size, IPC_CREAT | IPC_EXCL);
if (shmid < 0) {
printf("shmget failed: %d\n", errno);
return 1;
}
memAddress =3D shmat(shmid, NULL, 0);
if (memAddress =3D=3D (void *) -1) {
printf("shmat failed: %d\n", errno);
}
return 0;
}
I found out that shmget failed with ENOMEM in shmget_allocate_segment
(sysv_shm.c) because of an overflow of size (requested shared memory in
bytes):
int i, segnum, shmid, size;
...
size =3D round_page(uap->size);
if (shm_committed + btoc(size) > shminfo.shmall) {
return (ENOMEM);
}
When changing size to an unsigned long shmget works - but now shmat then
fails again with ENOMEM.
Is there any easy way to use a shared memory segment which is larger
than 2GB?
Kind regards,
Robert
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