Re: slab: start_cpu_timer/cache_reap CONFIG_HOTPLUG_CPU problems

From: Max Krasnyansky
Date: Tue Feb 20 2007 - 17:02:45 EST

Christoph Lameter wrote:
On Tue, 20 Feb 2007, Max Krasnyansky wrote:

I guess I kind of hijacked the thread. The second part of my first email was
dropped. Basically I was saying that I'm working on CPU isolation extensions.
Where an isolated CPU is not supposed to do much kernel work. In which case
you'd want to run slab cache reaper on some other CPU on behalf of the
one. Hence the proposal to explicitly pass cpu_id to the reaper. I guess now
that you guys fixed the hotplug case it does not help in that scenario.

A cpu must have a per cpu cache in order to do slab allocations. The locking in the slab allocator depends on it.

If the isolated cpus have no need for slab allocations then you will also not need to run the slab_reaper().

Ok. Sounds like disabling cache_reaper is a better option for now. Like you said
it's unlikely that slabs will grow much if that cpu is not heavily used by the

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