On Mon, Mar 28, 2016 at 08:05:41PM -0500, Christoph Lameter wrote: > On Mon, 28 Mar 2016, js1304@xxxxxxxxx wrote: > > > From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> > > > > Slab color isn't needed to be changed strictly. Because locking > > for changing slab color could cause more lock contention so this patch > > implements racy access/modify the slab color. This is a preparation step > > to implement lockless allocation path when there is no free objects in > > the kmem_cache. > > Acked-by: Christoph Lameter <cl@xxxxxxxxx> > > The rest of the description does not relate to this patch and does not > actually reflect the improvement of applying this patch. Remove the rest? No, below improvement is for this individual patch. Thanks. > > > > Below is the result of concurrent allocation/free in slab allocation > > benchmark made by Christoph a long time ago. I make the output simpler. > > The number shows cycle count during alloc/free respectively so less > > is better. > > > > * Before > > Kmalloc N*alloc N*free(32): Average=365/806 > > Kmalloc N*alloc N*free(64): Average=452/690 > > Kmalloc N*alloc N*free(128): Average=736/886 > > Kmalloc N*alloc N*free(256): Average=1167/985 > > Kmalloc N*alloc N*free(512): Average=2088/1125 > > Kmalloc N*alloc N*free(1024): Average=4115/1184 > > Kmalloc N*alloc N*free(2048): Average=8451/1748 > > Kmalloc N*alloc N*free(4096): Average=16024/2048 > > > > * After > > Kmalloc N*alloc N*free(32): Average=355/750 > > Kmalloc N*alloc N*free(64): Average=452/812 > > Kmalloc N*alloc N*free(128): Average=559/1070 > > Kmalloc N*alloc N*free(256): Average=1176/980 > > Kmalloc N*alloc N*free(512): Average=1939/1189 > > Kmalloc N*alloc N*free(1024): Average=3521/1278 > > Kmalloc N*alloc N*free(2048): Average=7152/1838 > > Kmalloc N*alloc N*free(4096): Average=13438/2013 > > > > It shows that contention is reduced for object size >= 1024 > > and performance increases by roughly 15%. > > > > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> > > --- > > mm/slab.c | 26 +++++++++++++------------- > > 1 file changed, 13 insertions(+), 13 deletions(-) > > > > diff --git a/mm/slab.c b/mm/slab.c > > index df11757..52fc5e3 100644 > > --- a/mm/slab.c > > +++ b/mm/slab.c > > @@ -2536,20 +2536,7 @@ static int cache_grow(struct kmem_cache *cachep, > > } > > local_flags = flags & (GFP_CONSTRAINT_MASK|GFP_RECLAIM_MASK); > > > > - /* Take the node list lock to change the colour_next on this node */ > > check_irq_off(); > > - n = get_node(cachep, nodeid); > > - spin_lock(&n->list_lock); > > - > > - /* Get colour for the slab, and cal the next value. */ > > - offset = n->colour_next; > > - n->colour_next++; > > - if (n->colour_next >= cachep->colour) > > - n->colour_next = 0; > > - spin_unlock(&n->list_lock); > > - > > - offset *= cachep->colour_off; > > - > > if (gfpflags_allow_blocking(local_flags)) > > local_irq_enable(); > > > > @@ -2570,6 +2557,19 @@ static int cache_grow(struct kmem_cache *cachep, > > if (!page) > > goto failed; > > > > + n = get_node(cachep, nodeid); > > + > > + /* Get colour for the slab, and cal the next value. */ > > + n->colour_next++; > > + if (n->colour_next >= cachep->colour) > > + n->colour_next = 0; > > + > > + offset = n->colour_next; > > + if (offset >= cachep->colour) > > + offset = 0; > > + > > + offset *= cachep->colour_off; > > + > > /* Get slab management. */ > > freelist = alloc_slabmgmt(cachep, page, offset, > > local_flags & ~GFP_CONSTRAINT_MASK, nodeid); > > > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@xxxxxxxxx. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>