On Wed 02-03-16 14:20:38, Jerry Lee wrote: > Hi, > > I have a x86_64 system with 2G RAM using linux-3.12.x. During copying > large > files (e.g. 100GB), kswapd easily consumes 100% CPU until the file is > deleted > or the page cache is dropped. With setting the min_free_kbytes from 16384 > to > 65536, the symptom is mitigated but I can't totally get rid of the problem. > > After some trial and error, I found that highest zone is always unbalanced > with > order-0 page request so that pgdat_blanaced() continuously return false and > kswapd can't sleep. > > Here's the watermarks (min_free_kbytes = 65536) in my system: > Node 0, zone DMA > pages free 2167 > min 138 > low 172 > high 207 > scanned 0 > spanned 4095 > present 3996 > managed 3974 > > Node 0, zone DMA32 > pages free 215375 > min 16226 > low 20282 > high 24339 > scanned 0 > spanned 1044480 > present 490971 > managed 464223 > > Node 0, zone Normal > pages free 7 > min 18 > low 22 > high 27 > scanned 0 > spanned 1536 > present 1536 > managed 523 The zone Normal is just too small and that confuses the reclaim path. > > Besides, when the kswapd crazily spins, the value of the following entries > in vmstat increases quickly even when I stop copying file: > > pgalloc_dma 17719 > pgalloc_dma32 3262823 > slabs_scanned 937728 > kswapd_high_wmark_hit_quickly 54333233 > pageoutrun 54333235 > > Is there anything I could do to totally get rid of the problem? I would try to sacrifice those few megs and get rid of zone normal completely. AFAIR mem=4G should limit the max_pfn to 4G so DMA32 should cover the shole memory. -- Michal Hocko SUSE Labs -- 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>