[linux-mm-cc] Questions about MemLimit

[Clemens Eisserer]

Hi Nitin,

Thanks for your very detailed reply, I hope I don't steal your time with this.

> Now, OrigDataSize staying constant suggests than all further writes seem to
> be going
> to backing swap device. This happens when either ComprDataSize reaches
> MemLimit
> or when incompressible pages are found.

This time I set memlimit to 350mb without backing swap and the same
load as before, and experienced the same - very high disk activity
(like swapping) when memory was starting to get tight.
Could it be this time, because compcache reports only 350mb swap space
to be on the safe side and now the kernel notices its low on swap and
does something strange?

My personal wish would be, all pages would stay in memory, until
there's no space left, and the least recently used pages are stored in
the backing swap.
Because compressible or not, a disk read is a disk read, which I would
like to avoid using it as a memory compressor. However I am not a
memory management expert ;)


Thanks again for this really cool project, Clemens


[root at localhost compcache-0.5.3]# free
             total       used       free     shared    buffers     cached
Mem:        511948     507064       4884          0       2320      52288
-/+ buffers/cache:     452456      59492
Swap:       349996     310188      39808


[root at localhost compcache-0.5.3]# cat /proc/ramzswap
DiskSize:         350000 kB
NumReads:         266752
NumWrites:        156405
FailedReads:           0
FailedWrites:          0
InvalidIO:             0
PagesDiscard:          0
ZeroPages:          6307
GoodCompress:         70 %
NoCompress:            3 %
PagesStored:       80893
PagesUsed:         30837
OrigDataSize:     323572 kB
ComprDataSize:    120493 kB
MemUsedTotal:     123348 kB