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 AE5536B7718 for ; Thu, 6 Sep 2018 01:41:59 -0400 (EDT) Received: by mail-ed1-f72.google.com with SMTP id c25-v6so3150167edb.12 for ; Wed, 05 Sep 2018 22:41:59 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id w37-v6si3390749edb.15.2018.09.05.22.41.58 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 05 Sep 2018 22:41:58 -0700 (PDT) Date: Thu, 6 Sep 2018 07:41:57 +0200 From: Michal Hocko Subject: Re: [PATCH 2/2] mm: Create non-atomic version of SetPageReserved for init use Message-ID: <20180906054157.GI14951@dhcp22.suse.cz> References: <20180904181550.4416.50701.stgit@localhost.localdomain> <20180904183345.4416.76515.stgit@localhost.localdomain> <20180905062428.GV14951@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: Alexander Duyck Cc: linux-mm , LKML , "Duyck, Alexander H" , pavel.tatashin@microsoft.com, Andrew Morton , Ingo Molnar , "Kirill A. Shutemov" On Wed 05-09-18 13:18:24, Alexander Duyck wrote: > On Tue, Sep 4, 2018 at 11:24 PM Michal Hocko wrote: > > > > On Tue 04-09-18 11:33:45, Alexander Duyck wrote: > > > From: Alexander Duyck > > > > > > It doesn't make much sense to use the atomic SetPageReserved at init time > > > when we are using memset to clear the memory and manipulating the page > > > flags via simple "&=" and "|=" operations in __init_single_page. > > > > > > This patch adds a non-atomic version __SetPageReserved that can be used > > > during page init and shows about a 10% improvement in initialization times > > > on the systems I have available for testing. > > > > I agree with Dave about a comment is due. I am also quite surprised that > > this leads to such a large improvement. Could you be more specific about > > your test and machines you were testing on? > > So my test case has been just initializing 4 3TB blocks of persistent > memory with a few trace_printk values added to track total time in > move_pfn_range_to_zone. > > What I have been seeing is that the time needed for the call drops on > average from 35-36 seconds down to around 31-32. This information belongs to the changelog. > > > Other than that the patch makes sense to me. > > > > > Signed-off-by: Alexander Duyck > > > > With the above addressed, feel free to add > > Acked-by: Michal Hocko > > > > Thanks! > > As far as adding a comment are we just talking about why it is > reserved, or do we need a description of the __SetPageReserved versus > SetPageReserved. For now I was looking at adding a comment like: the later. The reason why we make it reserved should be quite clear. A comment wouldn't hurt of course and what you have is a good start. But it is usually atomic vs. non-atomic SetPage$Foo which needs some clarification. > @@ -5517,8 +5517,13 @@ void __meminit memmap_init_zone(unsigned long > size, int nid, unsigned long zone, > not_early: > page = pfn_to_page(pfn); > __init_single_page(page, pfn, zone, nid); > + > + /* > + * Mark page reserved as it will need to wait for onlining > + * phase for it to be fully associated with a zone. > + */ > if (context == MEMMAP_HOTPLUG) > - SetPageReserved(page); > + __SetPageReserved(page); > > /* > * Mark the block movable so that blocks are reserved for > > Any thoughts on this? > > Thanks. > > - Alex -- Michal Hocko SUSE Labs