Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756689Ab2JWIHb (ORCPT ); Tue, 23 Oct 2012 04:07:31 -0400 Received: from mx2.parallels.com ([64.131.90.16]:57601 "EHLO mx2.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751728Ab2JWIH1 (ORCPT ); Tue, 23 Oct 2012 04:07:27 -0400 Message-ID: <50865024.60309@parallels.com> Date: Tue, 23 Oct 2012 12:07:00 +0400 From: Glauber Costa User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:16.0) Gecko/20121016 Thunderbird/16.0.1 MIME-Version: 1.0 To: JoonSoo Kim CC: Christoph Lameter , , , Pekka Enberg , "David Rientjes" Subject: Re: [PATCH 2/2] slab: move kmem_cache_free to common code References: <1350914737-4097-1-git-send-email-glommer@parallels.com> <1350914737-4097-3-git-send-email-glommer@parallels.com> <0000013a88eff593-50da3bb8-3294-41db-9c32-4e890ef6940a-000000@email.amazonses.com> <508561E0.5000406@parallels.com> In-Reply-To: Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1866 Lines: 53 On 10/23/2012 04:48 AM, JoonSoo Kim wrote: > Hello, Glauber. > > 2012/10/23 Glauber Costa : >> On 10/22/2012 06:45 PM, Christoph Lameter wrote: >>> On Mon, 22 Oct 2012, Glauber Costa wrote: >>> >>>> + * kmem_cache_free - Deallocate an object >>>> + * @cachep: The cache the allocation was from. >>>> + * @objp: The previously allocated object. >>>> + * >>>> + * Free an object which was previously allocated from this >>>> + * cache. >>>> + */ >>>> +void kmem_cache_free(struct kmem_cache *s, void *x) >>>> +{ >>>> + __kmem_cache_free(s, x); >>>> + trace_kmem_cache_free(_RET_IP_, x); >>>> +} >>>> +EXPORT_SYMBOL(kmem_cache_free); >>>> + >>> >>> This results in an additional indirection if tracing is off. Wonder if >>> there is a performance impact? >>> >> if tracing is on, you mean? >> >> Tracing already incurs overhead, not sure how much a function call would >> add to the tracing overhead. >> >> I would not be concerned with this, but I can measure, if you have any >> specific workload in mind. > > With this patch, kmem_cache_free() invokes __kmem_cache_free(), > that is, it add one more "call instruction" than before. > > I think that Christoph's comment means above fact. Ah, this. Ok, I got fooled by his mention to tracing. I do agree, but since freeing is ultimately dependent on the allocator layout, I don't see a clean way of doing this without dropping tears of sorrow around. The calls in slub/slab/slob would have to be somehow inlined. Hum... maybe it is possible to do it from include/linux/sl*b_def.h... Let me give it a try and see what I can come up with. -- 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/