Red Hat Bugzilla – Bug 202760
sysctl values too small for larger servers
Last modified: 2011-07-18 04:54:32 EDT
The Linux Kernel defaults of the following sysctl parameters are too small to
run larger applications. Values are taken from a server with 8 CPUs and 8 GB
RAM, running RHEL 4 AS Update 2, Kernel 2.6.9-22.0.2.ELsmp x86_64, assuming this
hasn't been changed yet:
1 # cat /proc/sys/kernel/shmmax
33554432 (32 MB)
2 # cat /proc/sys/kernel/shmall
2097152 (8 GB)
3 # cat /proc/sys/kernel/sem
250 32000 32 128
ad 1 and 2) We currently recommend values representing 20 GB each. My proposal
for new default values would be to dynamically adapt them to the available size
of virtual memory, by adding up RAM and Swap.
ad 3) There we recommend our customers to set 1250 256000 100 8192. Is there
also a possibility to adapt a new Kernel default dynamically to larger machines?
If you can't adapt the Kernel defaults, which values would you recommend to
cover even large machines? Think of something with 8 or more CPUs and 64 or more
GB of RAM...
SAP - can you verify that this is still an issue in RHEL 4.6?
Well, I haven't got any feedback yet from your side...
ad 1 and 2) In the meanwhile you increased those values on RHEL 5; nevertheless
on RHEL 4 the values are still too low.
ad 3) This question is still open
We cant make this kind of change to RHEL4 this late in the lifecycle.
Well, then why don't you fix it two years ago...
There were also some questions asked, which still haven't been answered by Red Hat yet.
RHEL4 is near the end of its lifecycle and on current RHEL5 and RHEL6 releases the default sysctl values are set to much higher values. Therefore I'm closing this bug.