Re: [ANNOUNCE] Minneapolis Cluster Summit, July 29-30

[Pavel Machek <pavel@suse.cz>]

Hi!

> > I don't see why it would be a problem to implement a "this task
> > facilitates page reclaim" flag for userspace tasks that would take
> > care of this as well as the kernel does.
> 
> Yes, that has been done before, and it works - userspace "block drivers"
> which permanently mark themselves as PF_MEMALLOC to avoid the obvious
> deadlocks.

> Note that you can achieve a similar thing in current 2.6 by acquiring
> realtime scheduling policy, but that's an artifact of some brainwave which
> a VM hacker happened to have and isn't a thing which should be relied upon.
> 
> A privileged syscall which allows a task to mark itself as one which
> cleans memory would make sense.

Does it work?

I mean, in kernel, we have some memory cleaners (say 5), and they
need, say, 1MB total reserved memory.

Now, if you add another task with PF_MEMALLOC. But now you'd need
1.2MB reserved memory, and you only have 1MB. Things are obviously
going to break at some point.
								Pavel
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