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Date: Thu, 30 Oct 2014 02:23:33 +0200 From: "Kirill A. Shutemov" <kirill@...temov.name> To: Alex Thorlton <athorlton@....com> Cc: Andi Kleen <andi@...stfloor.org>, linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>, Bob Liu <lliubbo@...il.com>, David Rientjes <rientjes@...gle.com>, "Eric W. Biederman" <ebiederm@...ssion.com>, Hugh Dickins <hughd@...gle.com>, Ingo Molnar <mingo@...hat.com>, Kees Cook <keescook@...omium.org>, "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Mel Gorman <mgorman@...e.de>, Oleg Nesterov <oleg@...hat.com>, Peter Zijlstra <peterz@...radead.org>, Rik van Riel <riel@...hat.com>, Thomas Gleixner <tglx@...utronix.de>, Vladimir Davydov <vdavydov@...allels.com>, linux-kernel@...r.kernel.org Subject: Re: [PATCH 0/4] Convert khugepaged to a task_work function 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@....com> 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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