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    SubjectRe: [Intel-gfx] [PATCH] drm/i915: Selectively enable self-reclaim
    On 01/07/10 04:24 AM, Linus Torvalds 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
    >>
    >> + mapping_gfp_mask (mapping) |
    >> + __GFP_COLD |
    >> + gfpmask);
    >>
    >> 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.
    >
    > .. and then I left out the one flag I _meant_ to have there, namely
    > __GFP_MOVABLE.
    >
    >> 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:
    >
    > In fact, I don't really see why we should use that mapping_gfp_mask()
    > at all, since all allocations should be going through that
    > i915_gem_object_get_pages() function anyway. So why not just change
    > that function to ignore the default gfp mask for the mapping, and just
    > use the mask that the o915 driver wants?
    >
    > Btw, why did it want to mark the pages reclaimable?
    >
    > Anyway, what I'm suggesting somebody who sees this test is just
    > something like the patch below (whitespace-damage - I'm cutting and
    > pasting, it's a trivial one-liner). Does this change any behavior?
    > Vefa?
    >
    > Linus

    Dear Linus,

    I made the code change you documented below to a vanilla 2.6.34 tree,
    compiled it and tested hibernate/thaw cycles. In total, I tested
    16 cycles, with 8 consecutive cycles in one installation (Debian Sid)
    and 8 consecutive cycles in another one (Fedora 13). For every cycle,
    I tried to run "old" and "new" programs, in terms of whether they were
    run in previous cycles. I tried a few extra cycles with uswsusp as well.

    Based on my testing, I am happy to report that the change you suggest
    fixes the "memory corruption (segfaults) after thaw" issue for me.
    I can't thank you enough times for this.

    Now, the obligatory question: Could we have this fix applied to 2.6.32,
    2.6.33 and 2.6.34 ?

    Thanks a lot again!

    M. Vefa Bicakci

    --- linux-2.6.34/drivers/gpu/drm/i915/i915_gem.c.orig 2010-07-01 17:47:30.000000000 +0000
    +++ linux-2.6.34/drivers/gpu/drm/i915/i915_gem.c 2010-07-01 17:54:03.000000000 +0000
    @@ -2312,7 +2312,7 @@
    mapping = inode->i_mapping;
    for (i = 0; i < page_count; i++) {
    page = read_cache_page_gfp(mapping, i,
    - mapping_gfp_mask (mapping) |
    + __GFP_HIGHMEM |
    __GFP_COLD |
    gfpmask);
    if (IS_ERR(page))


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