[linux-mm-cc] swap-device write failure under low memory

[Uma shankar]

>
> If you ever get too many write failures, its an indication that you
> have oversized ramzswap device. From what I have observed, swap write
> failure quickly lead to system hang. In ideal case, ramzswap should
> be able to dynamically resize based on cache hit-rate, system memory
> pressure etc., but all this is not yet done. So, for now, best would
> be to experiment a bit and get some idea of ramzswap disksize that helps
> your workload while still not getting into messy conditions like OOM,
> swap write failures.
>
> Thanks,
> Nitin
>

And also there is a small uncertainty  of  how many pages will be compressable.
A large Tmpfs file  may get overcommitted at the time of initial
creation ( because most pages
are compressable at that time)  , but may later induce OOM after a
later  file-data-update
if  many pages become uncompressable  after the update.  ( As of now,
75% of page-size
is the threshold in ramzswap. ).

I guess the problems with a large disksize value may be told to the
users  in the
Readme file.