RE: shmall on Linux recommendation
- From: Yong Huang <yong321@xxxxxxxxx>
- To: Dave.Herring@xxxxxxxxxx
- Date: Thu, 14 Jan 2010 09:25:41 -0800 (PST)
Dave,
I don't think it matters if you set shmall to a very large number. On my
RHEL 5.3 play box, I had
# sysctl -a | grep shmall
kernel.shmall = 4294967296
After I edited /etc/sysctl.conf:
# Controls the maximum number of shared memory segments, in pages
#kernel.shmall = 4294967296
kernel.shmall = 4294967296000000
I didn't do sysctl -p, but rebooted the box. After that, everything is
backup normal.
To me, it's just an artificial number like shmmax in the sense that
it has no other meaning than preventing you from creating something
above it. Shmmax caps the single segment size and shmall caps the
total SysV shared memory size in unit of page (regardless regular
4k or HugepageSize).
Yong Huang
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