Re: [PATCH] temporarily disable swap token on memory pressure

[Zwane Mwaikambo <zwane@arm.linux.org.uk>]

On Sat, 26 Nov 2005, Zwane Mwaikambo wrote:

> On Fri, 25 Nov 2005, Rik van Riel wrote:
> 
> > Some users (hi Zwane) have seen a problem when running a workload
> > that eats nearly all of physical memory - th system does an OOM
> > kill, even when there is still a lot of swap free.
> > 
> > I suspect the problem is that that big task is holding the swap
> > token, and the VM has a very hard time finding any other page in
> > the system that is swappable.  
> > 
> > Instead of ignoring the swap token when sc->priority reaches 0,
> > we could simply take the swap token away from the memory hog and
> > make sure we don't give it back to the memory hog for a few seconds.
> > 
> > This patch is untested, since I have not reproduced Zwane's problem
> > on my system.  I would like to see test results from anybody who is
> > running into this problem.
> > 
> > This patch is against today's git head.
> 
> Very nice! With this patch my job actually completed.
> 
> MemTotal:      2049180 kB
> MemFree:         15592 kB
> Buffers:          1516 kB
> Cached:          62972 kB
> SwapCached:     190512 kB
> Active:        1626228 kB
> Inactive:       361288 kB
> HighTotal:           0 kB
> HighFree:            0 kB
> LowTotal:      2049180 kB
> LowFree:         15592 kB
> SwapTotal:     3228760 kB
> SwapFree:      2555688 kB
> Dirty:               0 kB
> Writeback:           0 kB
> Mapped:        1824108 kB
> Slab:            27392 kB
> CommitLimit:   4253348 kB
> Committed_AS:  2472188 kB
> PageTables:       6688 kB
> VmallocTotal: 34359738367 kB
> VmallocUsed:    263796 kB
> VmallocChunk: 34359474119 kB

Some information about the application;

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
 3974 root      25   0 2459m 1.7g 8588 R 99.9 88.2 118:38.43 simnow

root@morocco ~ {0:0} cat /proc/3974/maps | wc -l
73870

Lots of PAGE_SIZE mappings like so;

...
401a6c0000-401a6c1000 rwxp 401a6c0000 00:00 0
401a6c2000-401a6c3000 rwxp 401a6c2000 00:00 0
401a6c4000-401a6c5000 rwxp 401a6c4000 00:00 0
401a6c6000-401a6c7000 rwxp 401a6c6000 00:00 0
401a6c8000-401a6c9000 rwxp 401a6c8000 00:00 0
...

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