On Tue, Nov 03, 2009 at 11:01:50PM +0100, Frans Pop wrote: > On Monday 02 November 2009, Mel Gorman wrote: > > On Mon, Nov 02, 2009 at 06:32:54PM +0100, Frans Pop wrote: > > > On Monday 02 November 2009, Mel Gorman wrote: > > > > vmscan: Help debug kswapd issues by counting number of rewakeups and > > > > premature sleeps > > > > > > > > There is a growing amount of anedotal evidence that high-order > > > > atomic allocation failures have been increasing since 2.6.31-rc1. > > > > The two strongest possibilities are a marked increase in the number > > > > of GFP_ATOMIC allocations and alterations in timing. Debugging > > > > printk patches have shown for example that kswapd is sleeping for > > > > shorter intervals and going to sleep when watermarks are still not > > > > being met. > > > > > > > > This patch adds two kswapd counters to help identify if timing is an > > > > issue. The first counter kswapd_highorder_rewakeup counts the number > > > > of times that kswapd stops reclaiming at one order and restarts at a > > > > higher order. The second counter kswapd_slept_prematurely counts the > > > > number of times kswapd went to sleep when the high watermark was not > > > > met. > > > > > > What testing would you like done with this patch? > > > > Same reproduction as before except post what the contents of > > /proc/vmstat were after the problem was triggered. > > With a representative test I get 0 for kswapd_slept_prematurely. > Tested with .32-rc6 + patches 1-3 + this patch. > Assuming the problem actually reproduced, can you still retest with the patch I posted as a follow-up and see if fast or slow premature sleeps are happening and if the problem still occurs please? It's still possible with the patch as-is could be timing related. After I posted this patch, I continued testing and found I could get counts fairly reliably if kswapd was calling printk() before making the premature check so the window appears to be very small. -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- To unsubscribe from this list: send the line "unsubscribe kernel-testers" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
