From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qg0-f53.google.com (mail-qg0-f53.google.com [209.85.192.53]) by kanga.kvack.org (Postfix) with ESMTP id 5B1E96B0073 for ; Wed, 17 Jun 2015 10:30:27 -0400 (EDT) Received: by qged89 with SMTP id d89so15773983qge.0 for ; Wed, 17 Jun 2015 07:30:27 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id b69si4499863qgb.50.2015.06.17.07.30.26 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 17 Jun 2015 07:30:26 -0700 (PDT) Subject: [PATCH V2 5/6] slub: initial bulk free implementation From: Jesper Dangaard Brouer Date: Wed, 17 Jun 2015 16:29:24 +0200 Message-ID: <20150617142901.11791.19168.stgit@devil> In-Reply-To: <20150617142613.11791.76008.stgit@devil> References: <20150617142613.11791.76008.stgit@devil> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org, Christoph Lameter , Andrew Morton Cc: Joonsoo Kim , Jesper Dangaard Brouer This implements SLUB specific kmem_cache_free_bulk(). SLUB allocator now both have bulk alloc and free implemented. Choose to reenable local IRQs while calling slowpath __slab_free(). In worst case, where all objects hit slowpath call, the performance should still be faster than fallback function __kmem_cache_free_bulk(), because local_irq_{disable+enable} is very fast (7-cycles), while the fallback invokes this_cpu_cmpxchg() which is slightly slower (9-cycles). Nitpicking, this should be faster for N>=4, due to the entry cost of local_irq_{disable+enable}. Do notice that the save+restore variant is very expensive, this is key to why this optimization works. CPU: i7-4790K CPU @ 4.00GHz * local_irq_{disable,enable}: 7 cycles(tsc) - 1.821 ns * local_irq_{save,restore} : 37 cycles(tsc) - 9.443 ns Signed-off-by: Jesper Dangaard Brouer --- V2: - Add BUG_ON(!object) - No support for kmem_cache_debug() Measurements on CPU CPU i7-4790K @ 4.00GHz Baseline normal fastpath (alloc+free cost): 43 cycles(tsc) 10.834 ns Bulk- fallback - this-patch 1 - 58 cycles(tsc) 14.542 ns - 43 cycles(tsc) 10.811 ns improved 25.9% 2 - 50 cycles(tsc) 12.659 ns - 27 cycles(tsc) 6.867 ns improved 46.0% 3 - 48 cycles(tsc) 12.168 ns - 21 cycles(tsc) 5.496 ns improved 56.2% 4 - 47 cycles(tsc) 11.987 ns - 24 cycles(tsc) 6.038 ns improved 48.9% 8 - 46 cycles(tsc) 11.518 ns - 17 cycles(tsc) 4.280 ns improved 63.0% 16 - 45 cycles(tsc) 11.366 ns - 17 cycles(tsc) 4.483 ns improved 62.2% 30 - 45 cycles(tsc) 11.433 ns - 18 cycles(tsc) 4.531 ns improved 60.0% 32 - 75 cycles(tsc) 18.983 ns - 58 cycles(tsc) 14.586 ns improved 22.7% 34 - 71 cycles(tsc) 17.940 ns - 53 cycles(tsc) 13.391 ns improved 25.4% 48 - 80 cycles(tsc) 20.077 ns - 65 cycles(tsc) 16.268 ns improved 18.8% 64 - 71 cycles(tsc) 17.799 ns - 53 cycles(tsc) 13.440 ns improved 25.4% 128 - 91 cycles(tsc) 22.980 ns - 79 cycles(tsc) 19.899 ns improved 13.2% 158 - 100 cycles(tsc) 25.241 ns - 90 cycles(tsc) 22.732 ns improved 10.0% 250 - 102 cycles(tsc) 25.583 ns - 95 cycles(tsc) 23.916 ns improved 6.9% mm/slub.c | 34 +++++++++++++++++++++++++++++++++- 1 file changed, 33 insertions(+), 1 deletion(-) diff --git a/mm/slub.c b/mm/slub.c index 02c33bacd3a6..6ac5921b3389 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -2753,7 +2753,39 @@ EXPORT_SYMBOL(kmem_cache_free); /* Note that interrupts must be enabled when calling this function. */ void kmem_cache_free_bulk(struct kmem_cache *s, size_t size, void **p) { - __kmem_cache_free_bulk(s, size, p); + struct kmem_cache_cpu *c; + struct page *page; + int i; + + /* Debugging fallback to generic bulk */ + if (kmem_cache_debug(s)) + return __kmem_cache_free_bulk(s, size, p); + + local_irq_disable(); + c = this_cpu_ptr(s->cpu_slab); + + for (i = 0; i < size; i++) { + void *object = p[i]; + + BUG_ON(!object); + page = virt_to_head_page(object); + BUG_ON(s != page->slab_cache); /* Check if valid slab page */ + + if (c->page == page) { + /* Fastpath: local CPU free */ + set_freepointer(s, object, c->freelist); + c->freelist = object; + } else { + c->tid = next_tid(c->tid); + local_irq_enable(); + /* Slowpath: overhead locked cmpxchg_double_slab */ + __slab_free(s, page, object, _RET_IP_); + local_irq_disable(); + c = this_cpu_ptr(s->cpu_slab); + } + } + c->tid = next_tid(c->tid); + local_irq_enable(); } EXPORT_SYMBOL(kmem_cache_free_bulk); -- 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