From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f171.google.com (mail-pf0-f171.google.com [209.85.192.171]) by kanga.kvack.org (Postfix) with ESMTP id 921A96B0268 for ; Mon, 28 Mar 2016 01:27:34 -0400 (EDT) Received: by mail-pf0-f171.google.com with SMTP id x3so128949218pfb.1 for ; Sun, 27 Mar 2016 22:27:34 -0700 (PDT) Received: from mail-pa0-x22f.google.com (mail-pa0-x22f.google.com. [2607:f8b0:400e:c03::22f]) by mx.google.com with ESMTPS id z23si17846386pfi.42.2016.03.27.22.27.33 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 27 Mar 2016 22:27:33 -0700 (PDT) Received: by mail-pa0-x22f.google.com with SMTP id td3so89743958pab.2 for ; Sun, 27 Mar 2016 22:27:33 -0700 (PDT) From: js1304@gmail.com Subject: [PATCH 07/11] mm/slab: racy access/modify the slab color Date: Mon, 28 Mar 2016 14:26:57 +0900 Message-Id: <1459142821-20303-8-git-send-email-iamjoonsoo.kim@lge.com> In-Reply-To: <1459142821-20303-1-git-send-email-iamjoonsoo.kim@lge.com> References: <1459142821-20303-1-git-send-email-iamjoonsoo.kim@lge.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Christoph Lameter , Pekka Enberg , David Rientjes , Jesper Dangaard Brouer , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Joonsoo Kim From: Joonsoo Kim 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. 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 --- 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); -- 1.9.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org