Date: Mon, 17 Nov 2014 15:34:15 -0600
From: Alex Thorlton <athorlton@sgi.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Rik van Riel <riel@redhat.com>, Andi Kleen <andi@firstfloor.org>,
        Alex Thorlton <athorlton@sgi.com>, linux-mm@kvack.org,
        Andrew Morton <akpm@linux-foundation.org>, Bob Liu <lliubbo@gmail.com>,
        David Rientjes <rientjes@google.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Hugh Dickins <hughd@google.com>, Ingo Molnar <mingo@redhat.com>,
        Kees Cook <keescook@chromium.org>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Mel Gorman <mgorman@suse.de>, Oleg Nesterov <oleg@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Vladimir Davydov <vdavydov@parallels.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/4] Convert khugepaged to a task_work function
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On Fri, Oct 31, 2014 at 09:27:16PM +0100, Vlastimil Babka wrote:
> What could help would be to cache one or few free huge pages per
> zone with cache
> re-fill done asynchronously, e.g. via work queues. The cache could
> benefit fault-THP
> allocations as well. And adding some logic that if nobody uses the
> cached pages and
> memory is low, then free them. And importantly, if it's not possible
> to allocate huge
> pages for the cache, then prevent scanning for collapse candidates
> as there's no point.
> (well this is probably more complex if some nodes can allocate huge
> pages and others
> not).

I think this would be a pretty cool addition, even separately from this
effort.  If we keep a page cached on each NUMA node, then we could,
theoretically, really speed up the khugepaged scans (even if we don't
move those scans to task_work), and regular THP faults.  I'll add it to
my ever-growing wish list :)

- Alex
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