Re: Still OOM problems with 4.9er/4.10er kernels

[Gerhard Wiesinger]

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