>On Mon, May 19, 2014 at 07:15:38PM +0800, bhe at redhat.com wrote: > >[..] >> ------------------------------------------------- >> bhe# cat /etc/kdump.conf >> path /var/crash >> core_collector makedumpfile -E --message-level 1 -d 31 >> >> ------------------------------------------ >> kdump: dump target is /dev/sda2 >> kdump: saving [ 9.595153] EXT4-fs (sda2): re-mounted. Opts: >> data=ordered >> to /sysroot//var/crash/127.0.0.1-2014.05.19-18:50:18/ >> kdump: saving vmcore-dmesg.txt >> kdump: saving vmcore-dmesg.txt complete >> kdump: saving vmcore >> >> calculate_cyclic_buffer_size, get_free_memory_size: 68857856 >> >> Buffer size for the cyclic mode: 27543142 > >Bao, > >So 68857856 is 65MB. So we have around 65MB free when makedumpfile >started. > >27543142 is 26MB. So we reserved 26MB for bitmaps or we reserved >52MB for bitmaps? 52MB is correct, so the larry's view below looks right. >Looking at the backtrace, larry pointed out few things. > >- makedumpfile has already allocated around 52MB of anonymous memory. I > guess this primarily comes from bitmaps and looks like we are reserving > 52MB in bitmaps and not 26MB. I think this could be consistent with > current 80% logic as 80% of 65MB is around 52MB. > > [ 15.427173] Killed process 286 (makedumpfile) total-vm:79940kB, > anon-rss:54132kB, file-rss:892kB > >- So we are left with 65-52 = 13MB of total memory for kernel as well > as makedumpfile. > >- We have around 1500 pages in page cache which are in writeback stage. > That means around 6MB of pages are dirty and being written back to > disk. That means makedumpfile might not require lot of memory but > kernel does require free memory in dirty/writeback pages when dump > file is being written. > > [ 15.167732] unevictable:7137 dirty:2 writeback:1511 unstable:0 > >- Larry mentioend that there are around 5000 pages (20MB of memory) > sitting in file pages in page cache which ideally should be reclaimable. > It is not clear why that memory is not being reclaimed fast enough. > > [ 15.167732] active_file:2406 inactive_file:2533 isolated_file:0 > >So to me bottom line is that once the write out starts, kernel needs >memory for holding dirty and writeback pages in cache too. So we probably >are being too aggresive in allocating 80% of free memory for bitmaps. May >be we should drop it down to 50-60% of free memory for bitmaps. I don't disagree to changing the 80% limit but I prefer to remove such a percentage threshold because it's dependent on the environment. Actually, I think it makes this problem more complex. Now, thanks to page_is_buddy(), the performance degradation caused by multi-cycle processing looks very small according to the benchmark on 2TB memory: https://lkml.org/lkml/2013/3/26/914 This result means we don't need to make an effort to allocate the bitmap buffer as large as possible. So how about just setting a small fixed value like 5MB as a safety limit? It may be safer, and it will be easier to estimate the total memory usage of makedumpfile, so I think it's better way if the most users especially large machine users accept it. Thanks Atsushi Kumagai >> Copying data : [ 15.9 %] -[ 14.955468] >> makedumpfile invoked oom-killer: gfp_mask=0x10200da, order=0, >> oom_score_adj=0 >> [ 14.963876] makedumpfile cpuset=/ mems_allowed=0 >> [ 14.968723] CPU: 0 PID: 286 Comm: makedumpfile Not tainted >> 3.10.0-123.el7.x86_64 #1 >> [ 14.976606] Hardware name: Hewlett-Packard HP Z420 Workstation/1589, >> BIOS J61 v01.02 03/09/2012 >> [ 14.985567] ffff88002fedc440 00000000f650c592 ffff88002fcb57d0 >> ffffffff815e19ba >> [ 14.993291] ffff88002fcb5860 ffffffff815dd02d ffffffff810b68f8 >> ffff8800359dc0c0 >> [ 15.001013] ffffffff00000206 ffffffff00000000 0000000000000000 >> ffffffff81102e03 >> [ 15.008733] Call Trace: >> [ 15.011413] [<ffffffff815e19ba>] dump_stack+0x19/0x1b >> [ 15.016778] [<ffffffff815dd02d>] dump_header+0x8e/0x214 >> [ 15.022321] [<ffffffff810b68f8>] ? ktime_get_ts+0x48/0xe0 >> [ 15.028036] [<ffffffff81102e03>] ? proc_do_uts_string+0xe3/0x130 >> [ 15.034383] [<ffffffff8114520e>] oom_kill_process+0x24e/0x3b0 >> [ 15.040446] [<ffffffff8106af3e>] ? has_capability_noaudit+0x1e/0x30 >> [ 15.047068] [<ffffffff81145a36>] out_of_memory+0x4b6/0x4f0 >> [ 15.052864] [<ffffffff8114b579>] __alloc_pages_nodemask+0xa09/0xb10 >> [ 15.059482] [<ffffffff81188779>] alloc_pages_current+0xa9/0x170 >> [ 15.065711] [<ffffffff811419f7>] __page_cache_alloc+0x87/0xb0 >> [ 15.071804] [<ffffffff81142606>] >> grab_cache_page_write_begin+0x76/0xd0 >> [ 15.078646] [<ffffffffa02aa133>] ext4_da_write_begin+0xa3/0x330 >> [ext4] >> [ 15.085495] [<ffffffff8114162e>] >> generic_file_buffered_write+0x11e/0x290 >> [ 15.092504] [<ffffffff81143785>] >> __generic_file_aio_write+0x1d5/0x3e0 >> [ 15.099294] [<ffffffff81050f00>] ? >> rbt_memtype_copy_nth_element+0xa0/0xa0 >> [ 15.106385] [<ffffffff811439ed>] generic_file_aio_write+0x5d/0xc0 >> [ 15.112841] [<ffffffffa02a0189>] ext4_file_write+0xa9/0x450 [ext4] >> [ 15.119321] [<ffffffff8117997c>] ? free_vmap_area_noflush+0x7c/0x90 >> [ 15.125884] [<ffffffff811af36d>] do_sync_write+0x8d/0xd0 >> [ 15.131492] [<ffffffff811afb0d>] vfs_write+0xbd/0x1e0 >> [ 15.136839] [<ffffffff811b0558>] SyS_write+0x58/0xb0 >> [ 15.142091] [<ffffffff815f2119>] system_call_fastpath+0x16/0x1b >> [ 15.148293] Mem-Info: >> [ 15.150770] Node 0 DMA per-cpu: >> [ 15.154138] CPU 0: hi: 0, btch: 1 usd: 0 >> [ 15.159133] Node 0 DMA32 per-cpu: >> [ 15.162741] CPU 0: hi: 42, btch: 7 usd: 12 >> [ 15.167732] active_anon:14395 inactive_anon:1034 isolated_anon:0 >> [ 15.167732] active_file:2406 inactive_file:2533 isolated_file:0 >> [ 15.167732] unevictable:7137 dirty:2 writeback:1511 unstable:0 >> [ 15.167732] free:488 slab_reclaimable:2371 slab_unreclaimable:3533 >> [ 15.167732] mapped:1110 shmem:1065 pagetables:166 bounce:0 >> [ 15.167732] free_cma:0 >> [ 15.203076] Node 0 DMA free:508kB min:4kB low:4kB high:4kB >> active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB >> unevictabs >> [ 15.242882] lowmem_reserve[]: 0 128 128 128 >> [ 15.247447] Node 0 DMA32 free:1444kB min:1444kB low:1804kB >> high:2164kB active_anon:57580kB inactive_anon:4136kB active_file:9624kB >> inacts >> [ 15.292683] lowmem_reserve[]: 0 0 0 0 >> [ 15.296761] Node 0 DMA: 1*4kB (U) 1*8kB (U) 1*16kB (U) 1*32kB (U) >> 1*64kB (U) 1*128kB (U) 1*256kB (U) 0*512kB 0*1024kB 0*2048kB 0*4096kB B >> [ 15.310372] Node 0 DMA32: 78*4kB (UEM) 52*8kB (UEM) 17*16kB (UM) >> 12*32kB (UM) 2*64kB (UM) 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*40B >> [ 15.324412] Node 0 hugepages_total=0 hugepages_free=0 >> hugepages_surp=0 hugepages_size=2048kB >> [ 15.333088] 13144 total pagecache pages >> [ 15.337161] 0 pages in swap cache >> [ 15.340708] Swap cache stats: add 0, delete 0, find 0/0 >> [ 15.346165] Free swap = 0kB >> [ 15.349280] Total swap = 0kB >> [ 15.353385] 90211 pages RAM >> [ 15.356420] 53902 pages reserved >> [ 15.359880] 6980 pages shared >> [ 15.363088] 29182 pages non-shared >> [ 15.366719] [ pid ] uid tgid total_vm rss nr_ptes swapents >> oom_score_adj name >> [ 15.374788] [ 85] 0 85 13020 553 24 0 >> 0 systemd-journal >> [ 15.383818] [ 134] 0 134 8860 547 22 0 >> -1000 systemd-udevd >> [ 15.392664] [ 146] 0 146 5551 245 23 0 >> 0 plymouthd >> [ 15.401167] [ 230] 0 230 3106 537 16 0 >> 0 dracut-pre-pivo >> [ 15.410181] [ 286] 0 286 19985 13756 55 0 >> 0 makedumpfile >> [ 15.418942] Out of memory: Kill process 286 (makedumpfile) score 368 >> or sacrifice child >> [ 15.427173] Killed process 286 (makedumpfile) total-vm:79940kB, >> anon-rss:54132kB, file-rss:892kB >> //lib/dracut/hooks/pre-pivot/9999-kdump.sh: line >> Generating "/run/initramfs/rdsosreport.txt" >> >> > >> > >> > Thanks >> > Atsushi Kumagai >> >
