Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S376159AbXEEBlI (ORCPT ); Fri, 4 May 2007 21:41:08 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1031416AbXEEBlI (ORCPT ); Fri, 4 May 2007 21:41:08 -0400 Received: from netops-testserver-4-out.sgi.com ([192.48.171.29]:39383 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1031094AbXEEBlH (ORCPT ); Fri, 4 May 2007 21:41:07 -0400 Date: Fri, 4 May 2007 18:41:05 -0700 (PDT) From: Christoph Lameter X-X-Sender: clameter@schroedinger.engr.sgi.com To: Tim Chen cc: "Chen, Tim C" , "Siddha, Suresh B" , "Zhang, Yanmin" , "Wang, Peter Xihong" , Arjan van de Ven , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: RE: Regression with SLUB on Netperf and Volanomark In-Reply-To: <1178322176.23795.219.camel@localhost.localdomain> Message-ID: References: <9D2C22909C6E774EBFB8B5583AE5291C02786032@fmsmsx414.amr.corp.intel.com> <1178298897.23795.195.camel@localhost.localdomain> <1178318609.23795.214.camel@localhost.localdomain> <1178322176.23795.219.camel@localhost.localdomain> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4417 Lines: 144 If you want to test some more: Here is a patch that removes the atomic ops from the allocation patch. But I only see minor improvements on my amd64 box here. Avoid the use of atomics in slab_alloc This only increases netperf performance by 1%. Wonder why? What we do is add the last free field in the page struct to setup a separate per cpu freelist. From that one we can allocate without taking the slab lock because we checkout the complete list of fre objects when we first touch the slab. This allows concurrent allocations and frees from the same slab using two mutually exclusive freelists. If the allocator is running out of its per cpu freelist then it will consult the per slab freelist and reload if objects were freed in it. Signed-off-by: Christoph Lameter --- include/linux/mm_types.h | 5 ++++- mm/slub.c | 44 +++++++++++++++++++++++++++++++++++--------- 2 files changed, 39 insertions(+), 10 deletions(-) Index: slub/include/linux/mm_types.h =================================================================== --- slub.orig/include/linux/mm_types.h 2007-05-04 17:39:33.000000000 -0700 +++ slub/include/linux/mm_types.h 2007-05-04 17:58:38.000000000 -0700 @@ -50,9 +50,12 @@ struct page { spinlock_t ptl; #endif struct { /* SLUB uses */ - struct page *first_page; /* Compound pages */ + void **active_freelist; /* Allocation freelist */ struct kmem_cache *slab; /* Pointer to slab */ }; + struct { + struct page *first_page; /* Compound pages */ + }; }; union { pgoff_t index; /* Our offset within mapping. */ Index: slub/mm/slub.c =================================================================== --- slub.orig/mm/slub.c 2007-05-04 17:40:50.000000000 -0700 +++ slub/mm/slub.c 2007-05-04 18:14:23.000000000 -0700 @@ -845,6 +845,7 @@ static struct page *new_slab(struct kmem page->offset = s->offset / sizeof(void *); page->slab = s; page->inuse = 0; + page->active_freelist = NULL; start = page_address(page); end = start + s->objects * s->size; @@ -1137,6 +1138,19 @@ static void putback_slab(struct kmem_cac */ static void deactivate_slab(struct kmem_cache *s, struct page *page, int cpu) { + /* Two freelists that are now to be consolidated */ + while (unlikely(page->active_freelist)) { + void **object; + + /* Retrieve object from active_freelist */ + object = page->active_freelist; + page->active_freelist = page->active_freelist[page->offset]; + + /* And put onto the regular freelist */ + object[page->offset] = page->freelist; + page->freelist = object; + page->inuse--; + } s->cpu_slab[cpu] = NULL; ClearPageActive(page); @@ -1206,25 +1220,32 @@ static void *slab_alloc(struct kmem_cach local_irq_save(flags); cpu = smp_processor_id(); page = s->cpu_slab[cpu]; - if (!page) + if (unlikely(!page)) goto new_slab; + if (likely(page->active_freelist)) { +fast_object: + object = page->active_freelist; + page->active_freelist = object[page->offset]; + local_irq_restore(flags); + return object; + } + slab_lock(page); if (unlikely(node != -1 && page_to_nid(page) != node)) goto another_slab; redo: - object = page->freelist; - if (unlikely(!object)) + if (unlikely(!page->freelist)) goto another_slab; if (unlikely(PageError(page))) goto debug; -have_object: - page->inuse++; - page->freelist = object[page->offset]; + /* Reload the active freelist */ + page->active_freelist = page->freelist; + page->freelist = NULL; + page->inuse = s->objects; slab_unlock(page); - local_irq_restore(flags); - return object; + goto fast_object; another_slab: deactivate_slab(s, page, cpu); @@ -1267,6 +1288,7 @@ have_slab: local_irq_restore(flags); return NULL; debug: + object = page->freelist; if (!alloc_object_checks(s, page, object)) goto another_slab; if (s->flags & SLAB_STORE_USER) @@ -1278,7 +1300,11 @@ debug: dump_stack(); } init_object(s, object, 1); - goto have_object; + page->freelist = object[page->offset]; + page->inuse++; + slab_unlock(page); + local_irq_restore(flags); + return object; } void *kmem_cache_alloc(struct kmem_cache *s, gfp_t gfpflags) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/