Deric Abel wrote:
All,
Recently we've been working with some share memory problems and we've notice
some strange numbers in the most current kernels of sles 10 sp2
on kernel 2.6.16.60-0.37_f594963d-default #1 SMP Mon Mar 23 13:39:48 UTC 2009
We see the following default settings:
r...@lnxfdts1:DCTEST1:~ # ipcs -l
------ Shared Memory Limits --------
max number of segments = 4096
max seg size (kbytes) = 3217741
max total shared memory (kbytes) = 8388608
min seg size (bytes) = 1
Which are expected, but on any later kernels-
2.6.16.60-0.39.3-default #1 SMP Mon May 11 11:46:34 UTC 2009
or
2.6.16.60-0.42.5-default #1 SMP Mon Aug 24 09:41:41 UTC 2009 (most current
kernel for sles10sp2)
We see
r...@lnxmaint:DCTEST1:~ # ipcs -l
------ Shared Memory Limits --------
max number of segments = 4096
max seg size (kbytes) = 18014398509481983
max total shared memory (kbytes) = 4611686018427386880
min seg size (bytes) = 1
I don't know about you, but that total shared memory can't be good to have that
large of a number. Is this a bug (or a feature ;) )?
Also reading around I see that the max total shared memory should be equal to
your actual memory and max seg size should be equal to 75-90% of your memory
(depending on if you are reading from oracle or db2)
Any thoughts or comments that might shed some light on this?
I don't know how much this illuminates the matter, but it's a useful
trick;-)
,18014398509481983[r...@bobtail ~]# printf '%x\n' 18014398509481983
3fffffffffffff
[r...@bobtail ~]# printf '%x\n' 4611686018427386880
3ffffffffffffc00
[r...@bobtail ~]#
--
Cheers
John
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