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SubjectRe: Inquiry: Should we remove "isolcpus= kernel boot option? (may have realtime uses)


Paul Jackson wrote:
> Andi wrote:
>> Right now the system boot could put pages from some daemon in there before any
>> cpusets are set up and there's no easy way to get them away again
>
> We (SGI) routinely handle that need with a custom init program,
> invoked with the init= parameter to the booting kernel, which
> sets up cpusets and then invokes the normal (real) init program
> in a cpuset configured to exclude those CPUs and nodes which we
> want to remain unloaded. For example, on a 256 CPU, 64 node
> system, we might have init running on a single node of 4 CPUs,
> and leave the remaining 63 nodes and 252 CPUs isolated from all
> the usual user level daemons started by init.
>
> There is no need for additional kernel changes to accomplish this.

You do not even need to replace /sbin/init for this, no ?
Simply installing custom
/etc/init.d/create_cpusets
with priority 0
# chkconfig: 12345 0 99
will do the job.

That script will move init itself into the appropriate cpuset and from then on
everything will inherit it.

Max


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