Re: [BUG] mm, thp: khugepaged can't allocate on requested node when confined to a cpuset

From: Rik van Riel
Date: Tue Oct 14 2014 - 11:31:59 EST

On 10/14/2014 10:54 AM, Peter Zijlstra wrote:
On Tue, Oct 14, 2014 at 02:48:28PM +0300, Kirill A. Shutemov wrote:

Why whould you want to pin khugpeaged? Is there a valid use-case?
Looks like userspace shoots to its leg.

Its just bad design to put so much work in another context. But the
use-case is isolating other cpus.

Is there a reason why we should respect cpuset limitation for kernel

Yes, because we want to allow isolating CPUs from 'random' activity.

Should we bypass cpuset for PF_KTHREAD completely?

No. That'll break stuff.

Agreed on the above.

I suspect the sane thing to do is allow a cpuset
limited task to still allocate pages elsewhere,
if it explicitly asks for it.

Ask for something potentially stupid? Get it :)

In many of the cases where something asks for memory
in a specific location, it has a good reason to do
so, and there's no reason to deny it.
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