On Sat, 15 Mar 2014 10:19:52 +0000 Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> wrote: > On Mon, Feb 17, 2014 at 09:09:54PM +0000, Russell King - ARM Linux wrote: > > On Mon, Feb 17, 2014 at 10:02:31PM +0100, Maxime Bizon wrote: > > > > > > On Sun, 2014-02-16 at 22:50 +0000, Russell King - ARM Linux wrote: > > > > > > > http://www.home.arm.linux.org.uk/~rmk/misc/log-20140208.txt > > > > > > [<c0064ce0>] (__alloc_pages_nodemask+0x0/0x694) from [<c022273c>] (sk_page_frag_refill+0x78/0x108) > > > [<c02226c4>] (sk_page_frag_refill+0x0/0x108) from [<c026a3a4>] (tcp_sendmsg+0x654/0xd1c) r6:00000520 r5:c277bae0 r4:c68f37c0 > > > [<c0269d50>] (tcp_sendmsg+0x0/0xd1c) from [<c028ca9c>] (inet_sendmsg+0x64/0x70) > > > > > > FWIW I had OOMs with the exact same backtrace on kirkwood platform > > > (512MB RAM), but sorry I don't have the full dump anymore. > > > > > > I found a slow leaking process, and since I fixed that leak I now have > > > uptime better than 7 days, *but* there was definitely some memory left > > > when the OOM happened, so it appears to be related to fragmentation. > > > > However, that's a side effect, not the cause - and a patch has been > > merged to fix that OOM - but that doesn't explain where most of the > > memory has gone! > > > > I'm presently waiting for the machine to OOM again (it's probably going > > to be something like another month) at which point I'll grab the files > > people have been mentioning (/proc/meminfo, /proc/vmallocinfo, > > /proc/slabinfo etc.) > > For those new to this report, this is a 3.12.6+ kernel, and I'm seeing > OOMs after a month or two of uptime. > > Last night, it OOM'd severely again at around 5am... and rebooted soon > after so we've lost any hope of recovering anything useful from the > machine. > > However, the new kernel re-ran the raid check, and... > > md: data-check of RAID array md2 > md: minimum _guaranteed_ speed: 1000 KB/sec/disk. > md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) > for data-check. > md: using 128k window, over a total of 4194688k. > md: delaying data-check of md3 until md2 has finished (they share one or more physical units) > md: delaying data-check of md4 until md2 has finished (they share one or more physical units) > md: delaying data-check of md3 until md2 has finished (they share one or more physical units) > md: delaying data-check of md5 until md2 has finished (they share one or more physical units) > md: delaying data-check of md3 until md2 has finished (they share one or more physical units) > md: delaying data-check of md4 until md2 has finished (they share one or more physical units) > md: delaying data-check of md6 until md2 has finished (they share one or more physical units) > md: delaying data-check of md4 until md2 has finished (they share one or more physical units) > md: delaying data-check of md3 until md2 has finished (they share one or more physical units) > md: delaying data-check of md5 until md2 has finished (they share one or more physical units) > md: md2: data-check done. > md: delaying data-check of md5 until md3 has finished (they share one or more physical units) > md: data-check of RAID array md3 > md: minimum _guaranteed_ speed: 1000 KB/sec/disk. > md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) > for data-check. > md: using 128k window, over a total of 524544k. > md: delaying data-check of md4 until md3 has finished (they share one or more physical units) > md: delaying data-check of md6 until md3 has finished (they share one or more physical units) > kmemleak: 836 new suspected memory leaks (see /sys/kernel/debug/kmemleak) > md: md3: data-check done. > md: delaying data-check of md6 until md4 has finished (they share one or more physical units) > md: delaying data-check of md4 until md5 has finished (they share one or more physical units) > md: data-check of RAID array md5 > md: minimum _guaranteed_ speed: 1000 KB/sec/disk. > md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) > for data-check. > md: using 128k window, over a total of 10486080k. > kmemleak: 2235 new suspected memory leaks (see /sys/kernel/debug/kmemleak) > md: md5: data-check done. > md: data-check of RAID array md4 > md: minimum _guaranteed_ speed: 1000 KB/sec/disk. > md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) > for data-check. > md: using 128k window, over a total of 10486080k. > md: delaying data-check of md6 until md4 has finished (they share one or more physical units) > kmemleak: 1 new suspected memory leaks (see /sys/kernel/debug/kmemleak) > md: md4: data-check done. > md: data-check of RAID array md6 > md: minimum _guaranteed_ speed: 1000 KB/sec/disk. > md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) > for data-check. > md: using 128k window, over a total of 10409472k. > kmemleak: 1 new suspected memory leaks (see /sys/kernel/debug/kmemleak) > kmemleak: 3 new suspected memory leaks (see /sys/kernel/debug/kmemleak) > md: md6: data-check done. > kmemleak: 1 new suspected memory leaks (see /sys/kernel/debug/kmemleak) > > which totals 3077 of leaks. So we have a memory leak. Looking at > the kmemleak file: > > unreferenced object 0xc3c3f880 (size 256): > comm "md2_resync", pid 4680, jiffies 638245 (age 8615.570s) > hex dump (first 32 bytes): > 00 00 00 00 00 00 00 00 00 00 00 00 01 00 00 f0 ................ > 00 00 00 00 10 00 00 00 00 00 00 00 00 00 00 00 ................ > backtrace: > [<c008d4f0>] __save_stack_trace+0x34/0x40 > [<c008d5f0>] create_object+0xf4/0x214 > [<c02da114>] kmemleak_alloc+0x3c/0x6c > [<c008c0d4>] __kmalloc+0xd0/0x124 > [<c00bb124>] bio_alloc_bioset+0x4c/0x1a4 > [<c021206c>] r1buf_pool_alloc+0x40/0x148 > [<c0061160>] mempool_alloc+0x54/0xfc > [<c0211938>] sync_request+0x168/0x85c > [<c021addc>] md_do_sync+0x75c/0xbc0 > [<c021b594>] md_thread+0x138/0x154 > [<c0037b48>] kthread+0xb0/0xbc > [<c0013190>] ret_from_fork+0x14/0x24 > [<ffffffff>] 0xffffffff > > with 3077 of these in the debug file. 3075 are for "md2_resync" and > two are for "md4_resync". > > /proc/slabinfo shows for this bucket: > kmalloc-256 3237 3450 256 15 1 : tunables 120 60 0 : slabdata 230 230 0 > > but this would only account for about 800kB of memory usage, which itself > is insignificant - so this is not the whole story. > > It seems that this is the culpret for the allocations: > for (j = pi->raid_disks ; j-- ; ) { > bio = bio_kmalloc(gfp_flags, RESYNC_PAGES); > > Since RESYNC_PAGES will be 64K/4K=16, each struct bio_vec is 12 bytes > (12 * 16 = 192) plus the size of struct bio, which would fall into this > bucket. > > I don't see anything obvious - it looks like it isn't every raid check > which loses bios. Not quite sure what to make of this right now. > I can't see anything obvious either. The bios allocated there are stored in a r1_bio and those pointers are never changed. If the r1_bio wasn't freed then when the data-check finished, mempool_destroy would complain that the pool wasn't completely freed. And when the r1_bio is freed, all the bios are put as well. I guess if something was calling bio_get() on the bio, then might stop the bio_put from freeing the memory, but I cannot see anything that would do that. I've tried testing on a recent mainline kernel and while kmemleak shows about 238 leaks from "swapper/0", there are none related to md or bios. I'll let it run a while longer and see if anything pops. NeilBrown
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