On Tue, 27 Dec 2011 06:50:08 +0400 "Nikolay S." <nowhere@xxxxxxxxxxxxxxxx> wrote: > В Вт., 27/12/2011 в 11:15 +0900, KAMEZAWA Hiroyuki пишет: > > On Sat, 24 Dec 2011 07:45:03 +1100 > > Dave Chinner <david@xxxxxxxxxxxxx> wrote: > > > > > On Fri, Dec 23, 2011 at 03:04:02PM +0400, nowhere wrote: > > > > В Пт., 23/12/2011 в 21:20 +1100, Dave Chinner пишет: > > > > > On Fri, Dec 23, 2011 at 01:01:20PM +0400, nowhere wrote: > > > > > > В Чт., 22/12/2011 в 09:55 +1100, Dave Chinner пишет: > > > > > > > On Wed, Dec 21, 2011 at 10:52:49AM +0100, Michal Hocko wrote: > > > > > > Here is the report of trace-cmd while dd'ing > > > > https://80.237.6.56/report-dd.xz > > > > > > Ok, it's not a shrink_slab() problem - it's just being called ~100uS > > > by kswapd. The pattern is: > > > > > > - reclaim 94 (batches of 32,32,30) pages from iinactive list > > > of zone 1, node 0, prio 12 > > > - call shrink_slab > > > - scan all caches > > > - all shrinkers return 0 saying nothing to shrink > > > - 40us gap > > > - reclaim 10-30 pages from inactive list of zone 2, node 0, prio 12 > > > - call shrink_slab > > > - scan all caches > > > - all shrinkers return 0 saying nothing to shrink > > > - 40us gap > > > - isolate 9 pages from LRU zone ?, node ?, none isolated, none freed > > > - isolate 22 pages from LRU zone ?, node ?, none isolated, none freed > > > - call shrink_slab > > > - scan all caches > > > - all shrinkers return 0 saying nothing to shrink > > > 40us gap > > > > > > And it just repeats over and over again. After a while, nid=0,zone=1 > > > drops out of the traces, so reclaim only comes in batches of 10-30 > > > pages from zone 2 between each shrink_slab() call. > > > > > > The trace starts at 111209.881s, with 944776 pages on the LRUs. It > > > finishes at 111216.1 with kswapd going to sleep on node 0 with > > > 930067 pages on the LRU. So 7 seconds to free 15,000 pages (call it > > > 2,000 pages/s) which is awfully slow.... > > > > > > vmscan gurus - time for you to step in now... > > > > > > > Can you show /proc/zoneinfo ? I want to know each zone's size. > Thanks, Qeustion: 1. does this system has no swap ? 2. What version of kernel which you didn't see the kswapd issue ? 3. Is this real host ? or virtualized ? > $ cat /proc/zoneinfo ... Node 0, zone DMA32 pages free 19620 min 14715 low 18393 high 22072 scanned 0 spanned 1044480 present 896960 nr_free_pages 19620 nr_inactive_anon 43203 nr_active_anon 206577 nr_inactive_file 412249 nr_active_file 126151 Then, DMA32(zone=1) files are enough large (> 32 << 12) Hmm. assuming all frees are used for file(of dd) (412249 + 126151 + 19620) >> 12 = 136 So, 32, 32, 30 scan seems to work as desgined. > Node 0, zone Normal > pages free 2854 > min 2116 > low 2645 > high 3174 > scanned 0 > spanned 131072 > present 129024 > nr_free_pages 2854 > nr_inactive_anon 20682 > nr_active_anon 10262 > nr_inactive_file 47083 > nr_active_file 11292 Hmm, NORMAL is much smaller than DMA32. (only 500MB.) Then, at priority=12, 13 << 12 = 53248 13 pages per a scan seems to work as designed. To me, it seems kswapd does usual work...reclaim small memory until free gets enough. And it seems 'dd' allocates its memory from ZONE_DMA32 because of gfp_t fallbacks. Memo. 1. why shrink_slab() should be called per zone, which is not zone aware. Isn't it enough to call it per priority ? 2. what spinlock contention that perf showed ? And if shrink_slab() doesn't consume cpu as trace shows, why perf says shrink_slab() is heavy.. 3. because 8/9 of memory is in DMA32, calling shrink_slab() frequently at scanning NORMAL seems to be time wasting. Thanks, -Kame -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>