[PATCH] makedumpfile: change the wrong code to calculate bufsize_cyclic for elf dump
bhe at redhat.com
bhe at redhat.com
Mon May 19 04:15:38 PDT 2014
Hi Astushi,
> No, 16MB was used for bitmaps also in my case.
> --cyclic-buffer option means specifying each bitmap size, so allocated bitmap
> size is the double of --cyclic-buffer.
> (But now, this behavior is only for ELF case, just the specified size is allocated
> in kdump case. Yes, it's confusing...)
>
> --cyclic-buffer buffer_size
> Specify the buffer size in kilo bytes for analysis in the cyclic
> mode. Actually, the double of buffer_size kilo bytes will be
> allocated in memory. In the cyclic mode, the number of cycles
> is represented as:
Yeah, I was wrong about this. If specified --cyclic-buffer doesn't
exceed the memory limit, it is equal to info->bufsize_cyclic. But for
elf dump, it need be double. E.g if free memory is 30M, --cyclic-buffer
is 16M, it will absolutely fail. But the code check here should be done
separately. Since it's meaningless for elf dump if 2 x --cyclic-buffer
exceeds the free memory.
if (info->bufsize_cyclic > free_memory) {
.......
{
I think code here need be changed.
>
> So only 456KB was the requirement for other purposes, 20% of available
> memory (3.5MB) was enough, thus the current assumption is safe even
> when available memory is only 17MB like my test.
>
> According to my test:
>
> http://lists.infradead.org/pipermail/kexec/2014-May/011784.html
>
> > Here is the result on a 2nd kernel environment:
> >
> > parameter | result
> > dump_lv | buffer[KiB] | mmap (=4MiB) | VmHWM [KiB]
> > --------+-------------+---------------+------------------
> > d31 | 1 | on | 776 // about 700
> > Ed31 | 1 | on | 712
> > d31 | 1 | off | 704
> > Ed31 | 1 | off | 708
> > d31 | 1000 | on | 1776 // about 700 + 1000
> > Ed31 | 1000 | on | 2716 // about 700 + 1000 * 2
> > d31 | 1000 | off | 1660
> > Ed31 | 1000 | off | 2556
>
> The requirement memory size for other purposes seems about 700KB when the dump
> level is 31, it's so small that we can ignore it.
> The size will increase by KB order based on the system memory size in practice
> (this assumption comes from my code investigation), but 6MB (20% of 30MB) still
> sounds much enough as safety limit.
> This is why I was wondering why OOM happened on your machine.
>
> Now that I heard that OOM happened only on nfs, I guess just nfs requires lots
> of memory. (I did my test only on local fs.)
> If we can get the required size, we could reflect it in the safety limit size.
>
> I haven't checked your test result below yet, so I'll mention it later.
>
> BTW, I prepared a temporal branch "oom" to investigate this issue,
> let's use this after this:
>
> http://sourceforge.net/p/makedumpfile/code/ci/oom/tree/
About OOM, I don't know why the difference between yours and mine is so
big. My test machine has 16G memory, and the reserved crashkernel=161M.
The OOM happened in a very high frequency. You can check the last
section of kdump failed log, OOM failed when use 80% for
info->bufsize_buffer though left free memory is 13M.
I changed the code like below.
---------------------------------------------------
diff --git a/makedumpfile.c b/makedumpfile.c
index 8dc1181..cd710a3 100644
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -3157,6 +3157,7 @@ out:
return FALSE;
if (info->flag_cyclic) {
+ printf("\ncalculate_cyclic_buffer_size,
get_free_memory_size: %llu\n", get_free_memory_size());
if (info->bufsize_cyclic == 0) {
if (!calculate_cyclic_buffer_size())
return FALSE;
@@ -3204,6 +3205,7 @@ out:
DEBUG_MSG("\n");
DEBUG_MSG("Buffer size for the cyclic mode: %ld\n",
info->bufsize_cyclic);
+ printf("\n Buffer size for the cyclic mode: %ld\n",
info->bufsize_cyclic);
}
if (!is_xen_memory() && !cache_init())
@@ -9060,7 +9062,7 @@ calculate_cyclic_buffer_size(void) {
if (info->num_dumpfile > 1)
bitmap_size /= info->num_dumpfile;
- info->bufsize_cyclic = MIN(limit_size, bitmap_size);
+ info->bufsize_cyclic = limit_size;
-------------------------------------------------
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
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
>
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