On Thu, Aug 18, 2011 at 4:18 AM, Pavel Ivanov [off-list ref] wrote:

quoted

quoted

Why "killing" does not appear here? Why it try to "find some
recently used page"?

Because killing is the last resort. As long as kernel can free
a page by dropping an unmodified file-backed page, it will do that.
When there is nothing more to drop, and still more free pages
are needed, _then_ kernel will start oom killing.

I have a little concern about this explanation of yours. Suppose we
have some amount of more or less actively executing processes in the
system. Suppose they started to use lots of resident memory. Amount of
memory they use is less than total available physical memory but when
we add total size of code for those processes it would be several
pages more than total size of physical memory. As I understood from
your explanation in such situation one process will execute its time
slice, kernel will switch to other one, find that its code was pushed
out of RAM, read it from disk, execute its time slice, switch to next
process, read its code from disk, execute and so on. So system will be
virtually unusable because of constantly reading from disk just to
execute next small piece of code. But oom will never be firing in such
situation. Is my understanding correct?

Yes.

Shouldn't it be considered as an unwanted behavior?

Yes. But all alternatives (such as killing some process) seem to be worse.

-- 
vda

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