Messages in this thread | | | Date | Fri, 4 Feb 2011 16:48:00 +0100 | From | Andrea Arcangeli <> | Subject | Re: khugepaged: gets stuck when writing to USB flash, 2.6.38-rc2 |
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On Thu, Feb 03, 2011 at 10:16:17PM +0100, Jindřich Makovička wrote: > On Thu, Feb 3, 2011 at 20:06, Andrea Arcangeli <aarcange@redhat.com> wrote: > > On Thu, Feb 03, 2011 at 01:24:08PM +0000, Mel Gorman wrote: > >> This is very likely. Compaction calls into migration which will wait on > >> dirty pages after a time. With a large number of dirty pages backed by a > >> slow drive such as a USB stick, it could be getting stalled there for a > >> long period of time. > >> > >> Whether migration sleeps or not can be controlled by the sync parameter > >> passed into try_to_compact_memory which could be always forced to false > >> if GFP_NO_KSWAPD? > > > > I would expect that to hide any regression we could have because of > > more dirty cache in the system, yes. > > > > However Jindřich reported not being able to reproduce anything anymore > > in -rc3, so I'm unsure if we should make that change anymore. I asked > > to try again cause it should too easy that got fixed magically > > I tried again and reproduced with -rc3 too, sorry for misinformation. > > I also tried echo never > /sys/kernel/mm/transparent_hugepage/defrag > , and it seems preventing the system freeze, but still the copying > itself sometimes comes to almost complete stop (GkrellM shows short > spikes of tens of kB/s on the USB /dev/sdX). In this case, khugepaged > is also in DN. I still didn't observe this problem when disabling THP > completely by echo never > enabled .
Ok then you may need this too:
echo never > /sys/kernel/mm/transparent_hugepage/khugepaged/defrag
Compaction is likely too heavy so we need to look into that. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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