On Fri, Apr 06, 2012 at 12:34:39PM -0700, Andrew Morton wrote: > On Wed, 28 Mar 2012 17:06:21 +0100 > Mel Gorman <mgorman@xxxxxxx> wrote: > > > (cc'ing active people in the thread "[patch 68/92] mm: forbid lumpy-reclaim > > in shrink_active_list()") > > > > In the interest of keeping my fingers from the flames at LSF/MM, I'm > > releasing an RFC for lumpy reclaim removal. > > I grabbed them, thanks. > There probably will be a V2 as Ying pointed out a problem with patch 1. > > > > ... > > > > MMTests Statistics: vmstat > > Page Ins 5426648 2840348 2695120 > > Page Outs 7206376 7854516 7860408 > > Swap Ins 36799 0 0 > > Swap Outs 76903 4 0 > > Direct pages scanned 31981 43749 160647 > > Kswapd pages scanned 26658682 1285341 1195956 > > Kswapd pages reclaimed 2248583 1271621 1178420 > > Direct pages reclaimed 6397 14416 94093 > > Kswapd efficiency 8% 98% 98% > > Kswapd velocity 22134.225 1127.205 1051.316 > > Direct efficiency 20% 32% 58% > > Direct velocity 26.553 38.367 141.218 > > Percentage direct scans 0% 3% 11% > > Page writes by reclaim 6530481 4 0 > > Page writes file 6453578 0 0 > > Page writes anon 76903 4 0 > > Page reclaim immediate 256742 17832 61576 > > Page rescued immediate 0 0 0 > > Slabs scanned 1073152 971776 975872 > > Direct inode steals 0 196279 205178 > > Kswapd inode steals 139260 70390 64323 > > Kswapd skipped wait 21711 1 0 > > THP fault alloc 1 126 143 > > THP collapse alloc 324 294 224 > > THP splits 32 8 10 > > THP fault fallback 0 0 0 > > THP collapse fail 5 6 7 > > Compaction stalls 364 1312 1324 > > Compaction success 255 343 366 > > Compaction failures 109 969 958 > > Compaction pages moved 265107 3952630 4489215 > > Compaction move failure 7493 26038 24739 > > > > ... > > > > Success rates are completely hosed for 3.4-rc1 which is almost certainly > > due to [fe2c2a10: vmscan: reclaim at order 0 when compaction is enabled]. I > > expected this would happen for kswapd and impair allocation success rates > > (https://lkml.org/lkml/2012/1/25/166) but I did not anticipate this much > > a difference: 95% less scanning, 43% less reclaim by kswapd > > > > In comparison, reclaim/compaction is not aggressive and gives up easily > > which is the intended behaviour. hugetlbfs uses __GFP_REPEAT and would be > > much more aggressive about reclaim/compaction than THP allocations are. The > > stress test above is allocating like neither THP or hugetlbfs but is much > > closer to THP. > > We seem to be thrashing around a bit with the performance, and we > aren't tracking this closely enough. > Yes. > What is kswapd efficiency? pages-relclaimed/pages-scanned? pages_reclaimed*100/pages_scanned > Why did it > increase so much? Lumpy reclaim increases the number of pages scanned in isolate_lru_pages() and that is what I was attributing it to. > Are pages which were reclaimed via prune_icache_sb() > included? If so, they can make a real mess of the scanning efficiency > metric. > I don't think so. For Kswapd efficiency, I'm using "kswapd_steal" from vmstat and that is updated by shrink_inactive_list and not the slab shrinker > The increase in PGINODESTEAL is remarkable. It seems to largely be a > transfer from kswapd inode stealing. Bad from a latency POV, at least. > What would cause this change? I'm playing catch-up at the moment and right now, I do not have a good explanation as to why it changed like this. The most likely explanation is that we are reclaiming fewer pages leading to more slab reclaim. -- Mel Gorman 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>