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Date: Sat, 5 Jan 2013 01:07:15 +0000 From: Eric Wong <normalperson@...t.net> To: Mel Gorman <mgorman@...e.de> Cc: linux-mm@...ck.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, Rik van Riel <riel@...hat.com>, Minchan Kim <minchan@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>, Linus Torvalds <torvalds@...ux-foundation.org> Subject: Re: ppoll() stuck on POLLIN while TCP peer is sending Mel Gorman <mgorman@...e.de> wrote: > On Wed, Jan 02, 2013 at 08:08:48PM +0000, Eric Wong wrote: > > Instead, I disabled THP+compaction under v3.7.1 and I've been unable to > > reproduce the issue without THP+compaction. > > > > Implying that it's stuck in compaction somewhere. It could be the case > that compaction alters timing enough to trigger another bug. You say it > tests differently depending on whether TCP or unix sockets are used > which might indicate multiple problems. However, lets try and see if > compaction is the primary problem or not. I've only managed to encounter this issue with TCP sockets. No luck reproducing the issue with Unix sockets, not even with 90K buffers as suggested by Eric Dumazet. This seems unique to TCP. Fwiw, I also tried going back to a 16K MTU on loopback a few days ago, but was still able to reproduce the issue, so commit 0cf833aefaa85bbfce3ff70485e5534e09254773 doesn't seem to be a culprit, either. > > As I mention in http://mid.gmane.org/20121229113434.GA13336@dcvr.yhbt.net > > I run my below test (`toosleepy') with heavy network and disk activity > > for a long time before hitting this. > > > > Using a 3.7.1 or 3.8-rc2 kernel, can you reproduce the problem and then > answer the following questions please? OK, I'm on 3.8-rc2. > 1. What are the contents of /proc/vmstat at the time it is stuck? nr_free_pages 1998 nr_inactive_anon 3401 nr_active_anon 3349 nr_inactive_file 94361 nr_active_file 10929 nr_unevictable 0 nr_mlock 0 nr_anon_pages 6643 nr_mapped 2255 nr_file_pages 105400 nr_dirty 44 nr_writeback 0 nr_slab_reclaimable 0 nr_slab_unreclaimable 0 nr_page_table_pages 697 nr_kernel_stack 161 nr_unstable 0 nr_bounce 0 nr_vmscan_write 0 nr_vmscan_immediate_reclaim 0 nr_writeback_temp 0 nr_isolated_anon 0 nr_isolated_file 0 nr_shmem 114 nr_dirtied 1076168 nr_written 46330 nr_anon_transparent_hugepages 0 nr_free_cma 0 nr_dirty_threshold 22495 nr_dirty_background_threshold 11247 pgpgin 4398164 pgpgout 188556 pswpin 0 pswpout 0 pgalloc_dma 369887 pgalloc_dma32 28406230 pgalloc_normal 0 pgalloc_movable 0 pgfree 28779104 pgactivate 18160 pgdeactivate 17404 pgfault 34862559 pgmajfault 358 pgrefill_dma 14076 pgrefill_dma32 3328 pgrefill_normal 0 pgrefill_movable 0 pgsteal_kswapd_dma 12708 pgsteal_kswapd_dma32 917837 pgsteal_kswapd_normal 0 pgsteal_kswapd_movable 0 pgsteal_direct_dma 73 pgsteal_direct_dma32 4085 pgsteal_direct_normal 0 pgsteal_direct_movable 0 pgscan_kswapd_dma 12708 pgscan_kswapd_dma32 918789 pgscan_kswapd_normal 0 pgscan_kswapd_movable 0 pgscan_direct_dma 73 pgscan_direct_dma32 4115 pgscan_direct_normal 0 pgscan_direct_movable 0 pgscan_direct_throttle 0 pginodesteal 0 slabs_scanned 257024 kswapd_inodesteal 69910 kswapd_low_wmark_hit_quickly 2165 kswapd_high_wmark_hit_quickly 275 kswapd_skip_congestion_wait 0 pageoutrun 13412 allocstall 73 pgrotated 3 pgmigrate_success 448 pgmigrate_fail 0 compact_migrate_scanned 14860 compact_free_scanned 219867 compact_isolated 1652 compact_stall 33 compact_fail 10 compact_success 23 unevictable_pgs_culled 1058 unevictable_pgs_scanned 0 unevictable_pgs_rescued 1671 unevictable_pgs_mlocked 1671 unevictable_pgs_munlocked 1671 unevictable_pgs_cleared 0 unevictable_pgs_stranded 0 thp_fault_alloc 0 thp_fault_fallback 0 thp_collapse_alloc 0 thp_collapse_alloc_failed 0 thp_split 0 thp_zero_page_alloc 0 thp_zero_page_alloc_failed 0 > 2. What are the contents of /proc/PID/stack for every toosleepy > process when they are stuck? Oops, I needed a rebuild with CONFIG_STACKTRACE=y (it took some effort to get the right combination of options). I probably enabled a few more debugging options than I needed and it seems to have taken longer to reproduce the issue. Unfortunately I was distracted when toosleepy got stuck and missed the change to inspect before hitting ETIMEDOUT :x Attempting to reproduce the issue while I'm looking. > 3. Can you do a sysrq+m and post the resulting dmesg? SysRq : Show Memory Mem-Info: DMA per-cpu: CPU 0: hi: 0, btch: 1 usd: 0 CPU 1: hi: 0, btch: 1 usd: 0 DMA32 per-cpu: CPU 0: hi: 186, btch: 31 usd: 144 CPU 1: hi: 186, btch: 31 usd: 160 active_anon:3358 inactive_anon:3379 isolated_anon:0 active_file:10615 inactive_file:92319 isolated_file:0 unevictable:0 dirty:3 writeback:0 unstable:0 free:2240 slab_reclaimable:0 slab_unreclaimable:0 mapped:2333 shmem:114 pagetables:697 bounce:0 free_cma:0 DMA free:2408kB min:84kB low:104kB high:124kB active_anon:8kB inactive_anon:44kB active_file:824kB inactive_file:11512kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:15676kB managed:15900kB mlocked:0kB dirty:0kB writeback:0kB mapped:16kB shmem:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:112kB pagetables:20kB unstable:0kB bounce:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no lowmem_reserve[]: 0 489 489 489 DMA32 free:6552kB min:2784kB low:3480kB high:4176kB active_anon:13424kB inactive_anon:13472kB active_file:41636kB inactive_file:357764kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:500952kB managed:491396kB mlocked:0kB dirty:12kB writeback:0kB mapped:9316kB shmem:456kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:1160kB pagetables:2768kB unstable:0kB bounce:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no lowmem_reserve[]: 0 0 0 0 DMA: 52*4kB (UMR) 13*8kB (UMR) 4*16kB (R) 2*32kB (R) 1*64kB (R) 1*128kB (R) 1*256kB (R) 1*512kB (R) 1*1024kB (R) 0*2048kB 0*4096kB = 2424kB DMA32: 1608*4kB (UM) 15*8kB (M) 0*16kB 0*32kB 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 6552kB 103053 total pagecache pages 0 pages in swap cache Swap cache stats: add 0, delete 0, find 0/0 Free swap = 392188kB Total swap = 392188kB 131054 pages RAM 3477 pages reserved 283467 pages shared 111732 pages non-shared > What I'm looking for is a throttling bug (if pgscan_direct_throttle is > elevated), an isolated page accounting bug (nr_isolated_* is elevated > and process is stuck in congestion_wait in a too_many_isolated() loop) > or a free page accounting bug (big difference between nr_free_pages and > buddy list figures). > > I'll try reproducing this early next week if none of that shows an > obvious candidate. Thanks! I'll try to get you more information as soon as possible. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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