On 01/08/2015 02:04 AM, Simon Kirby wrote: > 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? Yes, the code using this counter is either treating it as signed, or includes a <0 tests. It's just the /proc output might be confusing here... >> > 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> > -- 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>