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Date: Fri, 10 Oct 2014 11:20:52 +0200 From: Peter Zijlstra <peterz@...radead.org> To: Alex Thorlton <athorlton@....com> Cc: linux-kernel@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>, Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>, Ingo Molnar <mingo@...nel.org>, "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Hugh Dickins <hughd@...gle.com>, Bob Liu <lliubbo@...il.com>, Johannes Weiner <hannes@...xchg.org>, linux-mm@...ck.org Subject: Re: [BUG] mm, thp: khugepaged can't allocate on requested node when confined to a cpuset On Wed, Oct 08, 2014 at 02:10:50PM -0500, Alex Thorlton wrote: > Is this particular bug a known issue? Its not unexpected for me. > I've been trying to come up with > a simple way to fix the bug, but it's a bit difficult since we no longer > have a way to trace back to the task_struct that we're collapsing for > once we've reached get_page_from_freelist. I'm wondering if we might > want to make the cpuset check higher up in the call-chain and then pass > that nodemask down instead of sending a NULL nodemask, as we end up > doing in many (most?) situations. I can think of several problems with > that approach as well, but it's all I've come up with so far. > > The obvious workaround is to not isolate khugepaged to a cpuset, but > since we're allowed to do so, I think the thread should probably behave > appropriately when pinned to a cpuset. > > Any input on this issue is greatly appreciated. Thanks, guys! So for the numa thing we do everything from the affected tasks context. There was a lot of arguments early on that that could never really work, but here we are. Should we convert khugepaged to the same? Drive the whole thing from task_work? That would make this issue naturally go away. -- 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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