Re: pg 8.1.3, AIX, huge box, painfully slow.

"Luke Lonergan" <llonergan(at)greenplum(dot)com> writes:
> On 4/7/06 3:27 PM, "Gavin Hamill" <gdh(at)laterooms(dot)com> wrote:

>> 278774: __semop(15728650, 0x0FFFFFFFFFFF7E80, 1) = 0
>> 155712: __semop(15728650, 0x0FFFFFFFFFFF5920, 1) = 0
>> 278774: __semop(15728649, 0x0FFFFFFFFFFF6F10, 1)

> Seems like you're hitting a very small target in RAM with these semop calls.

IIRC the address passed to semop() in our code is always a local struct
on the stack, so that's a bit of a red herring --- there won't be
cross-processor contention for that.

It's plausible though that we are seeing contention across members of
the LWLock array, with the semop storm just being a higher-level symptom
of the real hardware-level problem. You might try increasing
LWLOCK_PADDED_SIZE to 64 or even 128, see
src/backend/storage/lmgr/lwlock.c (this is something that does exist in
8.1, so it'd be easy to try).

regards, tom lane