From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx156.postini.com [74.125.245.156]) by kanga.kvack.org (Postfix) with SMTP id CBB3D6B0044 for ; Wed, 7 Nov 2012 02:04:29 -0500 (EST) Message-ID: <509A07E3.5090700@parallels.com> Date: Wed, 7 Nov 2012 08:04:03 +0100 From: Glauber Costa MIME-Version: 1.0 Subject: Re: [PATCH v6 19/29] memcg: infrastructure to match an allocation to the right cache References: <1351771665-11076-1-git-send-email-glommer@parallels.com> <1351771665-11076-20-git-send-email-glommer@parallels.com> <20121105162837.5fdac20c.akpm@linux-foundation.org> In-Reply-To: <20121105162837.5fdac20c.akpm@linux-foundation.org> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kamezawa.hiroyu@jp.fujitsu.com, Johannes Weiner , Tejun Heo , Michal Hocko , Christoph Lameter , Pekka Enberg , David Rientjes , Pekka Enberg , Suleiman Souhlal , JoonSoo Kim On 11/06/2012 01:28 AM, Andrew Morton wrote: > On Thu, 1 Nov 2012 16:07:35 +0400 > Glauber Costa wrote: > >> +static __always_inline struct kmem_cache * >> +memcg_kmem_get_cache(struct kmem_cache *cachep, gfp_t gfp) > > I still don't understand why this code uses __always_inline so much. > > I don't recall seeing the compiler producing out-of-line versions of > "static inline" functions (and perhaps it has special treatment for > functions which were defined in a header file?). > > And if the compiler *does* decide to uninline the function, perhaps it > knows best, and the function shouldn't have been declared inline in the > first place. > > > If it is indeed better to use __always_inline in this code then we have > a heck of a lot of other "static inline" definitions whcih we need to > convert! So, what's going on here? > The original motivation is indeed performance related. We want to make sure it is inline so it will figure out quickly the "I am not a memcg user" case and keep it going. The slub, for instance, is full of __always_inline functions to make sure that the fast path contains absolutely no function calls. So I was just following this here. I can remove the marker without a problem and leave it to the compiler if you think it is best -- 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