Very big shm area
Hello,
I wanted to know if it is possible to have a very big system V shared
memory segment (say about 1Gb) ?
I've quickly looked into the source code of shm.c and shm.h in ipc/ and
I've read the following:
/*
* SHMMAX, SHMMNI and SHMALL are upper limits are defaults which can
* be increased by sysctl
*/
But how far is it possible to increase them ? And which sysctl must be done ?
Thank you for answering,
Signature · 6 lines
** Gael Le Mignot "Kilobug", Ing3 EPITA - http://kilobug.free.fr ** Home Mail : [email protected] Work Mail : [email protected] GSM : 06.71.47.18.22 (in France) ICQ UIN : 7299959 Fingerprint : 1F2C 9804 7505 79DF 95E6 7323 B66B F67B 7103 C5DA "Software is like sex it's better when it's free.", Linus Torvalds
I run a Dell 6450 with 8GB ram and a 4GB SHMMAX. You can set the parameter any time through sysctl if you have it enabled, or you can hardcode it per the Oracle/DB2 Docs if you wish.
Austin
Quoted 15 lines · Kilobug
Hello,
I wanted to know if it is possible to have a very big system V shared
memory segment (say about 1Gb) ?I've quickly looked into the source code of
shm.candshm.hinipc/and
I've read the following:
/*
* SHMMAX, SHMMNI and SHMALL are upper limits are defaults which can
* be increased by sysctl
*/But how far is it possible to increase them ? And which sysctl must be done ?
Thank you for answering,
Quoted 4 lines · Kilobug
Hello,
I wanted to know if it is possible to have a very big system V shared memory segment (say about 1Gb) ?
I've quickly looked into the source code ofshm.candshm.hinipc/
Quoted 8 lines
and I've read the following:
/*
* SHMMAX, SHMMNI and SHMALL are upper limits are defaults which can
* be increased by sysctl
*/
But how far is it possible to increase them ? And which sysctl must be done ?
Thank you for answering,
ls /proc/sys/kernel/sh* and the names shouldn't be too tough from there. I'd be concerned about exercising this code on a virgin 2.4.17 as ISTR bugfixes for sysv ipc/shm cropping up in later kernel versions, though I can't say I've tracked this area very closely. Hopefully someone who does can chime in here and enlighten us both.
Cheers,
Bill
To get *good* performance from such a large SGA, it's best to use a -aa kernel I've found. Either 2.4.18-aa + whatever patches, or something similar. But there's been some fixes/changes/optimizations to the -aa tree with regards to large memory boxes.
I'm curious though how P4 HT will play into that performance on the new Xeons though. I'll have more to report in the next few weeks.
Quoted 28 lines · William Lee Irwin III
Quoted 4 lines · Kilobug
Hello,
I wanted to know if it is possible to have a very big system V shared memory segment (say about 1Gb) ?
I've quickly looked into the source code ofshm.candshm.hinipc/Quoted 8 lines
and I've read the following:
/*
* SHMMAX, SHMMNI and SHMALL are upper limits are defaults which can
* be increased by sysctl
*/
But how far is it possible to increase them ? And which sysctl must be done ?
Thank you for answering,ls
/proc/sys/kernel/sh*and the names shouldn't be too tough from there. I'd be concerned about exercising this code on a virgin 2.4.17 as ISTR bugfixes for sysv ipc/shm cropping up in later kernel versions, though I can't say I've tracked this area very closely. Hopefully someone who does can chime in here and enlighten us both.Cheers,
Bill
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