From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) by kanga.kvack.org (Postfix) with ESMTP id 6BF3D6B5365 for ; Thu, 29 Nov 2018 11:05:27 -0500 (EST) Received: by mail-ed1-f72.google.com with SMTP id i55so1319169ede.14 for ; Thu, 29 Nov 2018 08:05:27 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id m37sor1565066edd.6.2018.11.29.08.05.25 for (Google Transport Security); Thu, 29 Nov 2018 08:05:26 -0800 (PST) Date: Thu, 29 Nov 2018 16:05:24 +0000 From: Wei Yang Subject: Re: [PATCH] mm, show_mem: drop pgdat_resize_lock in show_mem() Message-ID: <20181129160524.ewjn2x7spyloitu4@master> Reply-To: Wei Yang References: <20181128210815.2134-1-richard.weiyang@gmail.com> <20181129081703.GN6923@dhcp22.suse.cz> <20181129150449.desiutez735agyau@master> <20181129154922.GT6923@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181129154922.GT6923@dhcp22.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Wei Yang , akpm@linux-foundation.org, jweiner@fb.com, linux-mm@kvack.org On Thu, Nov 29, 2018 at 04:49:22PM +0100, Michal Hocko wrote: >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. > Forgive my poor background knowledge, I went throught the code, but not found where call cond_resched. __remove_pages() release_mem_region_adjustable() clear_zone_contiguous() __remove_section() unregister_memory_section() __remove_zone() sparse_remove_one_section() set_zone_contiguous() Would you mind giving me a hint? >-- >Michal Hocko >SUSE Labs -- Wei Yang Help you, Help me