From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail190.messagelabs.com (mail190.messagelabs.com [216.82.249.51]) by kanga.kvack.org (Postfix) with ESMTP id 4AD988D0040 for ; Tue, 29 Mar 2011 21:05:37 -0400 (EDT) Date: Tue, 29 Mar 2011 18:06:11 -0700 From: Andrew Morton Subject: Re: [PATCH]mmap: add alignment for some variables Message-Id: <20110329180611.a71fe829.akpm@linux-foundation.org> In-Reply-To: <1301446882.3981.33.camel@sli10-conroe> References: <1301277536.3981.27.camel@sli10-conroe> <1301360054.3981.31.camel@sli10-conroe> <20110329152434.d662706f.akpm@linux-foundation.org> <1301446882.3981.33.camel@sli10-conroe> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Shaohua Li Cc: Andi Kleen , linux-mm , lkml , Rik van Riel , Hugh Dickins On Wed, 30 Mar 2011 09:01:22 +0800 Shaohua Li wrote: > +/* > + * Make sure vm_committed_as in one cacheline and not cacheline shared with > + * other variables. It can be updated by several CPUs frequently. > + */ > +struct percpu_counter vm_committed_as ____cacheline_internodealigned_in_smp; The mystery deepens. The only cross-cpu writeable fields in there are percpu_counter.lock and its companion percpu_counter.count. If CPUs are contending for the lock then that itself is a problem - how does adding some padding to the struct help anything? -- 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