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    SubjectRe: [GIT PULL v2] Early SLAB fixes for 2.6.31
    On Fri, 12 Jun 2009, Christoph Lameter wrote:
    > On Fri, 12 Jun 2009, Pekka J Enberg wrote:
    >
    > > @@ -3434,6 +3451,8 @@ __cache_alloc(struct kmem_cache *cachep, gfp_t flags, void *caller)
    > > unsigned long save_flags;
    > > void *objp;
    > >
    > > + flags &= slab_gfp_mask;
    > > +
    > > lockdep_trace_alloc(flags);
    > >
    > > if (slab_should_failslab(cachep, flags))
    >
    > Adds code to hot code path.
    >
    > > @@ -1595,6 +1601,8 @@ static __always_inline void *slab_alloc(struct kmem_cache *s,
    > > unsigned long flags;
    > > unsigned int objsize;
    > >
    > > + gfpflags &= slab_gfp_mask;
    > > +
    > > lockdep_trace_alloc(gfpflags);
    > > might_sleep_if(gfpflags & __GFP_WAIT);
    > >
    >
    > Adds code to hot code path.
    >
    > The allocators mask flags passed to the page allocator through
    > GFP_RECLAIM_MASK|GFP_CONSTRAINT_MASK. This is done outside of the critical
    > code paths.
    >
    > The might_sleep issues may be fixed by adding another check to
    > __might_sleep().

    How about something like this? There should be no extra code in fastpaths
    for production configs with this one.

    Pekka

    diff --git a/mm/slub.c b/mm/slub.c
    index 4d6004c..5e8cea1 100644
    --- a/mm/slub.c
    +++ b/mm/slub.c
    @@ -1613,6 +1613,8 @@ another_slab:
    deactivate_slab(s, c);

    new_slab:
    + gfpflags &= slab_gfp_mask;
    +
    new = get_partial(s, gfpflags, node);
    if (new) {
    c->page = new;
    @@ -1668,13 +1670,14 @@ static __always_inline void *slab_alloc(struct kmem_cache *s,
    struct kmem_cache_cpu *c;
    unsigned long flags;
    unsigned int objsize;
    + gfp_t real_gfp;

    - gfpflags &= slab_gfp_mask;
    + real_gfp = gfpflags & slab_gfp_mask;

    - lockdep_trace_alloc(gfpflags);
    - might_sleep_if(gfpflags & __GFP_WAIT);
    + lockdep_trace_alloc(real_gfp);
    + might_sleep_if(real_gfp & __GFP_WAIT);

    - if (should_failslab(s->objsize, gfpflags))
    + if (should_failslab(s->objsize, real_gfp))
    return NULL;

    local_irq_save(flags);

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      Last update: 2009-06-14 09:15    [W:0.022 / U:1.808 seconds]
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