The patch titled Subject: mm: slub: optimise the SLUB fast path to avoid pfmemalloc checks has been removed from the -mm tree. Its filename was mm-slub-optimise-the-slub-fast-path-to-avoid-pfmemalloc-checks.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Christoph Lameter <cl@xxxxxxxxx> Subject: mm: slub: optimise the SLUB fast path to avoid pfmemalloc checks This patch removes the check for pfmemalloc from the alloc hotpath and puts the logic after the election of a new per cpu slab. For a pfmemalloc page we do not use the fast path but force the use of the slow path which is also used for the debug case. This has the side-effect of weakening pfmemalloc processing in the following way; 1. A process that is allocating for network swap calls __slab_alloc. pfmemalloc_match is true so the freelist is loaded and c->freelist is now pointing to a pfmemalloc page. 2. A process that is attempting normal allocations calls slab_alloc, finds the pfmemalloc page on the freelist and uses it because it did not check pfmemalloc_match() The patch allows non-pfmemalloc allocations to use pfmemalloc pages with the kmalloc slabs being the most vunerable caches on the grounds they are most likely to have a mix of pfmemalloc and !pfmemalloc requests. A later patch will still protect the system as processes will get throttled if the pfmemalloc reserves get depleted but performance will not degrade as smoothly. [mgorman@xxxxxxx: Expanded changelog] Signed-off-by: Christoph Lameter <cl@xxxxxxxxx> Signed-off-by: Mel Gorman <mgorman@xxxxxxx> Cc: David Miller <davem@xxxxxxxxxxxxx> Cc: Neil Brown <neilb@xxxxxxx> Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> Cc: Mike Christie <michaelc@xxxxxxxxxxx> Cc: Eric B Munson <emunson@xxxxxxxxx> Cc: Eric Dumazet <eric.dumazet@xxxxxxxxx> Cc: Sebastian Andrzej Siewior <sebastian@xxxxxxxxxxxxx> Cc: Mel Gorman <mgorman@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/slub.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff -puN mm/slub.c~mm-slub-optimise-the-slub-fast-path-to-avoid-pfmemalloc-checks mm/slub.c --- a/mm/slub.c~mm-slub-optimise-the-slub-fast-path-to-avoid-pfmemalloc-checks +++ a/mm/slub.c @@ -2281,11 +2281,11 @@ new_slab: } page = c->page; - if (likely(!kmem_cache_debug(s))) + if (likely(!kmem_cache_debug(s) && pfmemalloc_match(page, gfpflags))) goto load_freelist; /* Only entered in the debug case */ - if (!alloc_debug_processing(s, page, freelist, addr)) + if (kmem_cache_debug(s) && !alloc_debug_processing(s, page, freelist, addr)) goto new_slab; /* Slab failed checks. Next slab needed */ deactivate_slab(s, page, get_freepointer(s, freelist)); @@ -2337,8 +2337,7 @@ redo: object = c->freelist; page = c->page; - if (unlikely(!object || !node_match(page, node) || - !pfmemalloc_match(page, gfpflags))) + if (unlikely(!object || !node_match(page, node))) object = __slab_alloc(s, gfpflags, node, addr, c); else { _ Patches currently in -mm which might be from cl@xxxxxxxxx are origin.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html