From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f198.google.com (mail-wr0-f198.google.com [209.85.128.198]) by kanga.kvack.org (Postfix) with ESMTP id 4BDA06B025F for ; Tue, 15 Aug 2017 18:09:52 -0400 (EDT) Received: by mail-wr0-f198.google.com with SMTP id g32so2807252wrd.8 for ; Tue, 15 Aug 2017 15:09:52 -0700 (PDT) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id 190si1901826wmj.143.2017.08.15.15.09.50 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 15 Aug 2017 15:09:50 -0700 (PDT) Date: Tue, 15 Aug 2017 15:09:47 -0700 From: Andrew Morton Subject: Re: [PATCH] swap: choose swap device according to numa node Message-Id: <20170815150947.9b7ccea78c5ea28ae88ba87f@linux-foundation.org> In-Reply-To: <20170815054944.GF2369@aaronlu.sh.intel.com> References: <20170814053130.GD2369@aaronlu.sh.intel.com> <20170814163337.92c9f07666645366af82aba2@linux-foundation.org> <20170815054944.GF2369@aaronlu.sh.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Aaron Lu Cc: linux-mm , lkml , "Chen, Tim C" , Huang Ying , "Kleen, Andi" , Michal Hocko , Minchan Kim On Tue, 15 Aug 2017 13:49:45 +0800 Aaron Lu wrote: > On Mon, Aug 14, 2017 at 04:33:37PM -0700, Andrew Morton wrote: > > On Mon, 14 Aug 2017 13:31:30 +0800 Aaron Lu wrote: > > > > > --- /dev/null > > > +++ b/Documentation/vm/swap_numa.txt > > > @@ -0,0 +1,18 @@ > > > +If the system has more than one swap device and swap device has the node > > > +information, we can make use of this information to decide which swap > > > +device to use in get_swap_pages() to get better performance. > > > + > > > +The current code uses a priority based list, swap_avail_list, to decide > > > +which swap device to use and if multiple swap devices share the same > > > +priority, they are used round robin. This change here replaces the single > > > +global swap_avail_list with a per-numa-node list, i.e. for each numa node, > > > +it sees its own priority based list of available swap devices. Swap > > > +device's priority can be promoted on its matching node's swap_avail_list. > > > + > > > +The current swap device's priority is set as: user can set a >=0 value, > > > +or the system will pick one starting from -1 then downwards. The priority > > > +value in the swap_avail_list is the negated value of the swap device's > > > +due to plist being sorted from low to high. The new policy doesn't change > > > +the semantics for priority >=0 cases, the previous starting from -1 then > > > +downwards now becomes starting from -2 then downwards and -1 is reserved > > > +as the promoted value. > > > > Could we please add a little "user guide" here? Tell people how to set > > up their system to exploit this? Sample /etc/fstab entries, perhaps? > > That's a good idea. > > How about this: > > ... > Looks good. Please send it along as a patch some time? > > I'm not sure what to do...any hint? > Adding a pr_err() perhaps? pr_emerg(), probably. Would it make sense to disable all swapon()s after this? -- 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