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From: Hillf Danton <hdanton@sina.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-mm <linux-mm@kvack.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Tim Murray <timmurray@google.com>,
	Joel Fernandes <joel@joelfernandes.org>,
	Suren Baghdasaryan <surenb@google.com>,
	Daniel Colascione <dancol@google.com>,
	Shakeel Butt <shakeelb@google.com>,
	Sonny Rao <sonnyrao@google.com>,
	Brian Geffon <bgeffon@google.com>
Subject: Re: [RFC 1/7] mm: introduce MADV_COOL
Date: Wed, 29 May 2019 16:52:00 +0800
Message-ID: <20190529085200.13444-1-hdanton@sina.com> (raw)


On Wed, 29 May 2019 13:05:52 +0800 Michal Hocko wrote:
> On Wed 29-05-19 10:40:33, Hillf Danton wrote:
> > On Wed, 29 May 2019 00:11:15 +0800 Michal Hocko wrote:
> > > On Tue 28-05-19 23:38:11, Hillf Danton wrote:
> > > > 
> > > > In short, I prefer to skip IO mapping since any kind of address range
> > > > can be expected from userspace, and it may probably cover an IO mapping.
> > > > And things can get out of control, if we reclaim some IO pages while
> > > > underlying device is trying to fill data into any of them, for instance.
> > > 
> > > What do you mean by IO pages why what is the actual problem?
> > > 
> > Io pages are the backing-store pages of a mapping whose vm_flags has
> > VM_IO set, and the comment in mm/memory.c says:
> >         /*
> >          * Physically remapped pages are special. Tell the
> >          * rest of the world about it:
> >          *   VM_IO tells people not to look at these pages
> >          *      (accesses can have side effects).
> > 
> 
> OK, thanks for the clarification of the first part of the question. Now
> to the second and the more important one. What is the actual concern?
> AFAIK those pages shouldn't be on LRU list.

The backing pages for GEM object are lru pages, see the function
drm_gem_get_pages() in drivers/gpu/drm/drm_gem.c, please.

> If they are then they should
> be safe to get reclaimed otherwise we would have a problem when
> reclaiming them on the normal memory pressure.

Yes, Sir, they could be swapped out.

> Why is this madvise any different?

Now, it is not, thanks to the light you are casting.

BR
Hillf


             reply index

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-29  8:52 Hillf Danton [this message]
  -- strict thread matches above, loose matches on Subject: below --
2019-05-29  2:40 Hillf Danton
2019-05-29  5:05 ` Michal Hocko
2019-05-28 15:38 Hillf Danton
2019-05-28 16:11 ` Michal Hocko
2019-05-28 12:15 Hillf Danton
2019-05-28 12:39 ` Minchan Kim
2019-05-20  3:52 [RFC 0/7] introduce memory hinting API for external process Minchan Kim
2019-05-20  3:52 ` [RFC 1/7] mm: introduce MADV_COOL Minchan Kim
2019-05-20  8:16   ` Michal Hocko
2019-05-20  8:19     ` Michal Hocko
2019-05-20 15:08       ` Suren Baghdasaryan
2019-05-20 22:55       ` Minchan Kim
2019-05-20 22:54     ` Minchan Kim
2019-05-21  6:04       ` Michal Hocko
2019-05-21  9:11         ` Minchan Kim
2019-05-21 10:05           ` Michal Hocko
2019-05-28  8:53   ` Hillf Danton
2019-05-28 10:58   ` Minchan Kim

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