From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f200.google.com (mail-pf0-f200.google.com [209.85.192.200]) by kanga.kvack.org (Postfix) with ESMTP id 15CD66B0069 for ; Thu, 19 Oct 2017 16:53:21 -0400 (EDT) Received: by mail-pf0-f200.google.com with SMTP id u27so6841163pfg.12 for ; Thu, 19 Oct 2017 13:53:21 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id q5si812930pgp.196.2017.10.19.13.53.19 for (version=TLS1 cipher=AES128-SHA bits=128/128); Thu, 19 Oct 2017 13:53:20 -0700 (PDT) Date: Thu, 19 Oct 2017 22:53:12 +0200 From: Michal Hocko Subject: Re: [PATCH] mm: mlock: remove lru_add_drain_all() Message-ID: <20171019205312.c4ghzdvk47oupvzl@dhcp22.suse.cz> References: <20171018231730.42754-1-shakeelb@google.com> <20171019123206.3etacullgnarbnad@dhcp22.suse.cz> <20171019193542.l5baqknxnfhljjkr@dhcp22.suse.cz> <20171019201306.u76wt3wgbt6sfhcj@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Shakeel Butt Cc: Andrew Morton , "Kirill A. Shutemov" , Vlastimil Babka , Joonsoo Kim , Minchan Kim , Yisheng Xie , Ingo Molnar , Greg Thelen , Hugh Dickins , Linux MM , LKML On Thu 19-10-17 13:14:52, Shakeel Butt wrote: > On Thu, Oct 19, 2017 at 1:13 PM, Michal Hocko wrote: > > On Thu 19-10-17 12:46:50, Shakeel Butt wrote: > >> > [...] > >> >> > >> >> Sorry for the confusion. I wanted to say that if the pages which are > >> >> being mlocked are on caches of remote cpus then lru_add_drain_all will > >> >> move them to their corresponding LRUs and then remaining functionality > >> >> of mlock will move them again from their evictable LRUs to unevictable > >> >> LRU. > >> > > >> > yes, but the point is that we are draining pages which might be not > >> > directly related to pages which _will_ be mlocked by the syscall. In > >> > fact those will stay on the cache. This is the primary reason why this > >> > draining doesn't make much sense. > >> > > >> > Or am I still misunderstanding what you are saying here? > >> > > >> > >> lru_add_drain_all() will drain everything irrespective if those pages > >> are being mlocked or not. > > > > yes, let me be more specific. lru_add_drain_all will drain everything > > that has been cached at the time mlock is called. And that is not really > > related to the memory which will be faulted in (and cached) and mlocked > > by the syscall itself. Does it make more sense now? > > > > Yes, you are absolutely right. Sorry for the confusion. So I think it would be much better to justify this change by arguing that paying a random overhead for something that doesn't relate to the work to be done is simply wrong. -- Michal Hocko SUSE Labs -- 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