From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx115.postini.com [74.125.245.115]) by kanga.kvack.org (Postfix) with SMTP id ED0E76B0082 for ; Fri, 18 May 2012 10:42:31 -0400 (EDT) Date: Fri, 18 May 2012 16:42:17 +0200 From: Jan Kara Subject: Re: [PATCH 1/2] lib: Proportions with flexible period Message-ID: <20120518144217.GC6875@quack.suse.cz> References: <1337096583-6049-1-git-send-email-jack@suse.cz> <1337096583-6049-2-git-send-email-jack@suse.cz> <1337291805.4281.97.camel@twins> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1337291805.4281.97.camel@twins> Sender: owner-linux-mm@kvack.org List-ID: To: Peter Zijlstra Cc: Jan Kara , Wu Fengguang , LKML , linux-mm@kvack.org On Thu 17-05-12 23:56:45, Peter Zijlstra wrote: > On Tue, 2012-05-15 at 17:43 +0200, Jan Kara wrote: > > +void fprop_fraction_percpu(struct fprop_global *p, > > + struct fprop_local_percpu *pl, > > + unsigned long *numerator, unsigned long *denominator) > > +{ > > + unsigned int seq; > > + s64 den; > > + > > + do { > > + seq = read_seqcount_begin(&p->sequence); > > + fprop_reflect_period_percpu(p, pl); > > + *numerator = percpu_counter_read_positive(&pl->events); > > + den = percpu_counter_read(&p->events); > > + if (den <= 0) > > + den = percpu_counter_sum(&p->events); > > + *denominator = den; > > + } while (read_seqcount_retry(&p->sequence, seq)); > > +} > > > why not use percpu_counter_read_positive(&p->events) and ditch > percpu_counter_sum()? That sum can be terribly expensive.. Yes. I'm actually not sure why I used the _sum here... Thanks for spotting this. Honza -- Jan Kara SUSE Labs, CR -- 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