From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f69.google.com (mail-wm0-f69.google.com [74.125.82.69]) by kanga.kvack.org (Postfix) with ESMTP id E0A716B02C3 for ; Tue, 4 Jul 2017 11:22:17 -0400 (EDT) Received: by mail-wm0-f69.google.com with SMTP id b20so24602007wmd.6 for ; Tue, 04 Jul 2017 08:22:17 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id j79si5639400wmf.14.2017.07.04.08.22.16 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 04 Jul 2017 08:22:16 -0700 (PDT) Date: Tue, 4 Jul 2017 08:22:06 -0700 From: Davidlohr Bueso Subject: Re: [patch V2 2/2] mm/memory-hotplug: Switch locking to a percpu rwsem Message-ID: <20170704152206.GB11168@linux-80c1.suse> References: <20170704093232.995040438@linutronix.de> <20170704093421.506836322@linutronix.de> <20170704150106.GA11168@linux-80c1.suse> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20170704150106.GA11168@linux-80c1.suse> Sender: owner-linux-mm@kvack.org List-ID: To: Thomas Gleixner , LKML , linux-mm@kvack.org, Andrey Ryabinin , Michal Hocko , Andrew Morton , Vlastimil Babka , Vladimir Davydov , Peter Zijlstra On Tue, 04 Jul 2017, Davidlohr Bueso wrote: >As a side effect you end up optimizing get/put_online_mems() at the cost >of more overhead for the actual hotplug operation, which is rare and of less >performance importance. So nm this, the reader side actually gets _more_ expensive with pcpu-rwsems due to at least two full barriers for each get/put operation. Thanks, Davidlohr -- 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