From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx125.postini.com [74.125.245.125]) by kanga.kvack.org (Postfix) with SMTP id 696518D0001 for ; Fri, 11 May 2012 10:42:40 -0400 (EDT) Message-ID: <1336747350.1017.22.camel@twins> Subject: Re: [PATCH 10/17] netvm: Allow skb allocation to use PFMEMALLOC reserves From: Peter Zijlstra Date: Fri, 11 May 2012 16:42:30 +0200 In-Reply-To: <20120511143218.GS11435@suse.de> References: <1336657510-24378-1-git-send-email-mgorman@suse.de> <1336657510-24378-11-git-send-email-mgorman@suse.de> <20120511.005740.210437168371869566.davem@davemloft.net> <20120511143218.GS11435@suse.de> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: quoted-printable Mime-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman Cc: David Miller , akpm@linux-foundation.org, linux-mm@kvack.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, neilb@suse.de, michaelc@cs.wisc.edu, emunson@mgebm.net On Fri, 2012-05-11 at 15:32 +0100, Mel Gorman wrote: > > > +extern atomic_t memalloc_socks; > > > +static inline int sk_memalloc_socks(void) > > > +{ > > > + return atomic_read(&memalloc_socks); > > > +} > >=20 > > Please change this to be a static branch. > >=20 >=20 > Will do. I renamed memalloc_socks to sk_memalloc_socks, made it a int as > atomics are unnecessary and I check it directly in a branch instead of a > static inline. It should be relatively easy for the branch predictor.=20 David means you to use include/linux/jump_label.h. static struct static_key sk_memalloc_socks =3D STATIC_KEY_INIT_FALSE; and have your function read: static inline bool sk_memalloc_socks(void) { return static_key_false(&sk_memalloc_socks); } which can be modified using: static_key_slow_inc(&sk_memalloc_socks); or static_key_slow_dec(&sk_memalloc_socks); This magic goo turns the branch into self-modifying code such that the branch is an unconditional jump at runtime. =20 -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org