Re: [PATCH 0/4] Convert khugepaged to a task_work function

[Kirill A. Shutemov]

On Wed, Oct 29, 2014 at 04:58:39PM -0500, Alex Thorlton wrote:
> On Tue, Oct 28, 2014 at 05:12:26AM -0700, Andi Kleen wrote:
> > Alex Thorlton <athorlton@xxxxxxx> writes:
> > 
> > > Last week, while discussing possible fixes for some unexpected/unwanted behavior
> > > from khugepaged (see: https://lkml.org/lkml/2014/10/8/515) several people
> > > mentioned possibly changing changing khugepaged to work as a task_work function
> > > instead of a kernel thread.  This will give us finer grained control over the
> > > page collapse scans, eliminate some unnecessary scans since tasks that are
> > > relatively inactive will not be scanned often, and eliminate the unwanted
> > > behavior described in the email thread I mentioned.
> > 
> > With your change, what would happen in a single threaded case?
> > 
> > Previously one core would scan and another would run the workload.
> > With your change both scanning and running would be on the same
> > core.
> > 
> > Would seem like a step backwards to me.
> 
> I suppose from the single-threaded point of view, it could be.  Maybe we
> could look at this a bit differently.  What if we allow processes to
> choose their collapse mechanism on fork?

Yet another knob nobody uses? Let's just do it right.

-- 
 Kirill A. Shutemov
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