On 16.03.2017 10:39, Michal Hocko wrote:
On Thu 16-03-17 02:23:18, lkml@xxxxxxxxxxx wrote:
On Thu, Mar 16, 2017 at 10:08:44AM +0100, Michal Hocko wrote:
On Thu 16-03-17 01:47:33, lkml@xxxxxxxxxxx wrote:
[...]
While on the topic of understanding allocation stalls, Philip Freeman recently
mailed linux-kernel with a similar report, and in his case there are plenty of
page cache pages. It was also a GFP_HIGHUSER_MOVABLE 0-order allocation.
care to point me to the report?
http://lkml.iu.edu/hypermail/linux/kernel/1703.1/06360.html
Thanks. It is gone from my lkml mailbox. Could you CC me (and linux-mm) please?
I'm no MM expert, but it appears a bit broken for such a low-order allocation
to stall on the order of 10 seconds when there's plenty of reclaimable pages,
in addition to mostly unused and abundant swap space on SSD.
yes this might indeed signal a problem.
Well maybe I missed something obvious that a better informed eye will catch.
Nothing really obvious. There is indeed a lot of anonymous memory to
swap out. Almost no pages on file LRU lists (active_file:759
inactive_file:749) but 158783 total pagecache pages so we have to have a
lot of pages in the swap cache. I would probably have to see more data
to make a full picture.
Why does the kernel prefer to swapin/out and not use
a.) the free memory?
b.) the buffer/cache?
There is ~100M memory available but kernel swaps all the time ...
Any ideas?
Kernel: 4.9.14-200.fc25.x86_64
top - 17:33:43 up 28 min, 3 users, load average: 3.58, 1.67, 0.89
Tasks: 145 total, 4 running, 141 sleeping, 0 stopped, 0 zombie
%Cpu(s): 19.1 us, 56.2 sy, 0.0 ni, 4.3 id, 13.4 wa, 2.0 hi, 0.3 si,
4.7 st
KiB Mem : 230076 total, 61508 free, 123472 used, 45096 buff/cache
procs -----------memory---------- ---swap-- -----io---- -system--
------cpu-----
r b swpd free buff cache si so bi bo in cs us sy
id wa st
3 5 303916 60372 328 43864 27828 200 41420 236 6984 11138 11
47 6 23 14
5 4 292852 52904 756 58584 19600 448 48780 540 8088 10528 18
61 1 7 13
3 3 288792 49052 1152 65924 4856 576 9824 1100 4324 5720 7
18 2 64 8
2 2 283676 54160 716 67604 6332 344 31740 964 3879 5055 12 34
10 37 7
3 3 286852 66712 216 53136 28064 4832 56532 4920 9175 12625 10
55 12 14 10
2 0 299680 62428 196 53316 36312 13164 54728 13212 16820 25283
7 56 18 12 7
1 1 300756 63220 624 58160 17944 1260 24528 1304 5804 9302 3
22 38 34 3
Thnx.
Ciao,
Gerhard
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