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    SubjectRe: [PATCH 1/5] mm: Add __GFP_NO_OOM_KILL flag
    Date
    On Monday 04 May 2009, David Rientjes wrote:
    > On Mon, 4 May 2009, Rafael J. Wysocki wrote:
    >
    > > > > Index: linux-2.6/mm/page_alloc.c
    > > > > ===================================================================
    > > > > --- linux-2.6.orig/mm/page_alloc.c
    > > > > +++ linux-2.6/mm/page_alloc.c
    > > > > @@ -1620,7 +1620,8 @@ nofail_alloc:
    > > > > }
    > > > >
    > > > > /* The OOM killer will not help higher order allocs so fail */
    > > > > - if (order > PAGE_ALLOC_COSTLY_ORDER) {
    > > > > + if (order > PAGE_ALLOC_COSTLY_ORDER ||
    > > > > + (gfp_mask & __GFP_NO_OOM_KILL)) {
    > > > > clear_zonelist_oom(zonelist, gfp_mask);
    > > > > goto nopage;
    > > > > }
    > > >
    > > > This is inconsistent because __GFP_NO_OOM_KILL now implies __GFP_NORETRY
    > > > (the "goto nopage" above), but only for allocations with __GFP_FS set and
    > > > __GFP_NORETRY clear.
    > >
    > > Well, what would you suggest?
    > >
    >
    > A couple things:
    >
    > - rebase this on mmotm so that it doesn't conflict with Mel Gorman's page
    > allocator speedup changes, and

    I'm going to rebase the patchset on top of linux-next eventually.

    > - avoid the final call to get_page_from_freelist() for
    > !(gfp_mask & __GFP_NO_OOM_KILL) by adding a check for it alongside
    > (gfp_mask & __GFP_FS) and !(gfp_mask & __GFP_NORETRY) because it should
    > really only catch parallel oom killings which won't happen in your
    > suspend case since it uses ALLOC_WMARK_HIGH.
    >
    > The latter is important to avoid unnecessary dependencies among low-level
    > __GFP_* flags (although all __GFP_NO_OOM_KILL allocations should really
    > all be passing __GFP_NORETRY too to avoid relying too heavily on direct
    > reclaim).

    OK, thanks.

    Something like this?

    ---
    include/linux/gfp.h | 3 ++-
    mm/page_alloc.c | 3 ++-
    2 files changed, 4 insertions(+), 2 deletions(-)

    Index: linux-2.6/mm/page_alloc.c
    ===================================================================
    --- linux-2.6.orig/mm/page_alloc.c
    +++ linux-2.6/mm/page_alloc.c
    @@ -1599,7 +1599,8 @@ nofail_alloc:
    zonelist, high_zoneidx, alloc_flags);
    if (page)
    goto got_pg;
    - } else if ((gfp_mask & __GFP_FS) && !(gfp_mask & __GFP_NORETRY)) {
    + } else if ((gfp_mask & __GFP_FS) && !(gfp_mask & __GFP_NORETRY)
    + && !(gfp_mask & __GFP_NO_OOM_KILL)) {
    if (!try_set_zone_oom(zonelist, gfp_mask)) {
    schedule_timeout_uninterruptible(1);
    goto restart;
    Index: linux-2.6/include/linux/gfp.h
    ===================================================================
    --- linux-2.6.orig/include/linux/gfp.h
    +++ linux-2.6/include/linux/gfp.h
    @@ -51,8 +51,9 @@ struct vm_area_struct;
    #define __GFP_THISNODE ((__force gfp_t)0x40000u)/* No fallback, no policies */
    #define __GFP_RECLAIMABLE ((__force gfp_t)0x80000u) /* Page is reclaimable */
    #define __GFP_MOVABLE ((__force gfp_t)0x100000u) /* Page is movable */
    +#define __GFP_NO_OOM_KILL ((__force gfp_t)0x200000u) /* Don't invoke out_of_memory() */

    -#define __GFP_BITS_SHIFT 21 /* Room for 21 __GFP_FOO bits */
    +#define __GFP_BITS_SHIFT 22 /* Number of __GFP_FOO bits */
    #define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1))

    /* This equals 0, but use constants in case they ever change */

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