On Mon, Jul 20, 2015 at 09:24:40PM +0200, Oleg Nesterov wrote:
> On 07/20, Oleg Nesterov wrote:
> >
> > But again, again, please ignore. This all is off-topic and my understanding
> > is very limited.
>
> Yes, yes, but sorry for noise and let me repeat...
>
> This memory lives in page-cache/lru, it is visible for shrinker which
> will unmap these pages for no reason on memory shortage. IOW, aio fools
> the kernel, this memory looks reclaimable but it is not. And we only do
> this for migration.
And we have the same problem with O_DIRECT. Given the size of the LRU in
a modern system, I highly doubt a handful of pages getting scanned is a
major problem. If you want to improve this, go ahead, but we need to
retain support for page migration as people have run into the need for it.
> Even if this is not a problem, this does not look right. So perhaps at
> least mapping_set_unevictable() makes sense. But I simply do not know
> if migration will work with this change.
Nor do I know if that will work.
> And I should have changes the subject a long ago... So what do you think
> we should do with the build failure?
I honestly don't care what of the options you do -- please just don't go
about adding BUG()s.
-ben
> Oleg.
--
"Thought is the essence of where you are now."
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