On Wed, Jan 07, 2015 at 10:48:10PM +0100, Vlastimil Babka wrote: > On 01/07/2015 10:28 PM, Simon Kirby wrote: > > > Hmm...A possibly-related issue...Before trying this, after a fresh boot, > > /proc/vmstat showed: > > > > nr_alloc_batch 4294541205 > > This can happen, and not be a problem in general. However, there was a fix > abe5f972912d086c080be4bde67750630b6fb38b in 3.17 for a potential performance > issue if this counter overflows on single processor configuration. It was marked > stable, but the 3.16 series was discontinued before the fix could be backported. > So if you are on single-core, you might hit the performance issue. That particular commit seems to just change the code path in that case, but should it be underflowing at all on UP? > > Still, nr_alloc_batch reads as 4294254379 after MySQL restart, and now > > seems to stay up there. > > Hm if it stays there, then you are probably hitting the performance issue. Look > at /proc/zoneinfo, which zone has the underflow. It means this zone will get > unfair amount of allocations, while others may contain stale data and would be > better candidates. In this case, it has only 640MB, and there's only DMA and Normal. This is affecting Normal, and DMA is so small that it probably doesn't matter. Simon- -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>