From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f71.google.com (mail-ed1-f71.google.com [209.85.208.71]) by kanga.kvack.org (Postfix) with ESMTP id 2297D6B5357 for ; Thu, 29 Nov 2018 10:49:26 -0500 (EST) Received: by mail-ed1-f71.google.com with SMTP id q8so1261930edd.8 for ; Thu, 29 Nov 2018 07:49:26 -0800 (PST) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id v27si1232206edm.111.2018.11.29.07.49.24 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 29 Nov 2018 07:49:24 -0800 (PST) Date: Thu, 29 Nov 2018 16:49:22 +0100 From: Michal Hocko Subject: Re: [PATCH] mm, show_mem: drop pgdat_resize_lock in show_mem() Message-ID: <20181129154922.GT6923@dhcp22.suse.cz> References: <20181128210815.2134-1-richard.weiyang@gmail.com> <20181129081703.GN6923@dhcp22.suse.cz> <20181129150449.desiutez735agyau@master> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181129150449.desiutez735agyau@master> Sender: owner-linux-mm@kvack.org List-ID: To: Wei Yang Cc: akpm@linux-foundation.org, jweiner@fb.com, linux-mm@kvack.org On Thu 29-11-18 15:04:49, Wei Yang wrote: > On Thu, Nov 29, 2018 at 09:17:03AM +0100, Michal Hocko wrote: > >On Thu 29-11-18 05:08:15, Wei Yang wrote: > >> Function show_mem() is used to print system memory status when user > >> requires or fail to allocate memory. Generally, this is a best effort > >> information and not willing to affect core mm subsystem. > > > >I would drop the part after and > > > >> The data protected by pgdat_resize_lock is mostly correct except there is: > >> > >> * page struct defer init > >> * memory hotplug > > > >This is more confusing than helpful. I would just drop it. > > > >The changelog doesn't explain what is done and why. The second one is > >much more important. I would say this > > > >" > >Function show_mem() is used to print system memory status when user > >requires or fail to allocate memory. Generally, this is a best effort > >information so any races with memory hotplug (or very theoretically an > >early initialization) should be toleratable and the worst that could > >happen is to print an imprecise node state. > > > >Drop the resize lock because this is the only place which might hold the > > As I mentioned in https://patchwork.kernel.org/patch/10689759/, there is > one place used in __remove_zone(). I don't get your suggestion of this > place. And is __remove_zone() could be called in IRQ context? It is only called from __remove_pages and that one calls cond_resched so obviosly not. -- Michal Hocko SUSE Labs