From mboxrd@z Thu Jan  1 00:00:00 1970
From: Chris Wilson <chris@chris-wilson.co.uk>
Subject: Re: [Intel-gfx] [PATCH] drm/i915: Selectively enable self-reclaim
Date: Thu, 01 Jul 2010 12:19:21 +0100
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On Wed, 30 Jun 2010 18:24:04 -0700, Linus Torvalds <torvalds@linux-foun=
dation.org> wrote:
> On Wed, Jun 30, 2010 at 4:07 PM, Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
> >
> > That commit changes the page cache allocation to use
> >
> > + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0=
 =C2=A0mapping_gfp_mask (mapping) |
> > + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0=
 =C2=A0__GFP_COLD |
> > + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0=
 =C2=A0gfpmask);
> >
> > if I read it right. And the default mapping_gfp_mask() is
> > GFP_HIGHUSER_MOVABLE, so I think you get all of
> > (__GFP_WAIT | __GFP_IO | __GFP_FS | __GFP_HARDWALL | __GFP_HIGHMEM)
> > set by default.
>=20
> .. and then I left out the one flag I _meant_ to have there, namely
> __GFP_MOVABLE.
>=20
> > The old code didn't just play games with ~__GFP_NORETRY and change
> > that at runtime (which was buggy - no locking, no protection, no
> > nothing), it also initialized the gfp mask. And that code also got
> > removed:

That code I added with the original shrinker patch, and the flags lifte=
d
from the shmem defaults, tweaked to what seemed sane with the addition =
of
NORETRY and friends. I see that i915 is unique in using shmem as the pa=
ge
allocator, which perhaps explains why this failure is not observed with
the ttm drivers. ttm uses two sets of gfp mask: HIGHUSER and USER | DMA=
32.
So replacing the mapping_gfp_mask() with HIGHUSER would seem appropriat=
e.
And the interaction of MOVABLE could explain why hibernate broke with t=
he
introduction of GEM.

* turns to his trusty copy of LDD to explain the various meanings of
gfp_t...
--=20
Chris Wilson, Intel Open Source Technology Centre