From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2993491AbdD3XOd (ORCPT ); Sun, 30 Apr 2017 19:14:33 -0400 Received: from mx1.redhat.com ([209.132.183.28]:40660 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2993398AbdD3XO2 (ORCPT ); Sun, 30 Apr 2017 19:14:28 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 953DB7F4AF Authentication-Results: ext-mx02.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx02.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=jglisse@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 953DB7F4AF Date: Sun, 30 Apr 2017 19:14:24 -0400 From: Jerome Glisse To: "Kirill A. Shutemov" Cc: Dan Williams , Ingo Molnar , "linux-kernel@vger.kernel.org" , Linux MM , Ingo Molnar , Andrew Morton , Logan Gunthorpe , Kirill Shutemov Subject: Re: [PATCH v2] mm, zone_device: replace {get, put}_zone_device_page() with a single reference Message-ID: <20170430231421.GA15163@redhat.com> References: <20170428063913.iz6xjcxblecofjlq@gmail.com> <149339998297.24933.1129582806028305912.stgit@dwillia2-desk3.amr.corp.intel.com> <1743017574.4309811.1493400875692.JavaMail.zimbra@redhat.com> <1579714997.4315035.1493402406629.JavaMail.zimbra@redhat.com> <1295710462.4327805.1493406971970.JavaMail.zimbra@redhat.com> <20170428193305.GA3912@redhat.com> <20170429101726.cdczojcjjupb7myy@node.shutemov.name> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20170429101726.cdczojcjjupb7myy@node.shutemov.name> User-Agent: Mutt/1.8.0 (2017-02-23) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Sun, 30 Apr 2017 23:14:28 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Apr 29, 2017 at 01:17:26PM +0300, Kirill A. Shutemov wrote: > On Fri, Apr 28, 2017 at 03:33:07PM -0400, Jerome Glisse wrote: > > On Fri, Apr 28, 2017 at 12:22:24PM -0700, Dan Williams wrote: > > > Are you sure about needing to hook the 2 -> 1 transition? Could we > > > change ZONE_DEVICE pages to not have an elevated reference count when > > > they are created so you can keep the HMM references out of the mm hot > > > path? > > > > 100% sure on that :) I need to callback into driver for 2->1 transition > > no way around that. If we change ZONE_DEVICE to not have an elevated > > reference count that you need to make a lot more change to mm so that > > ZONE_DEVICE is never use as fallback for memory allocation. Also need > > to make change to be sure that ZONE_DEVICE page never endup in one of > > the path that try to put them back on lru. There is a lot of place that > > would need to be updated and it would be highly intrusive and add a > > lot of special cases to other hot code path. > > Could you explain more on where the requirement comes from or point me to > where I can read about this. > HMM ZONE_DEVICE pages are use like other pages (anonymous or file back page) in _any_ vma. So i need to know when a page is freed ie either as result of unmap, exit or migration or anything that would free the memory. For zone device a page is free once its refcount reach 1 so i need to catch refcount transition from 2->1 This is the only way i can inform the device that the page is now free. See https://cgit.freedesktop.org/~glisse/linux/commit/?h=hmm-v21&id=52da8fe1a088b87b5321319add79e43b8372ed7d There is _no_ way around that. Cheers, Jérôme From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f199.google.com (mail-qk0-f199.google.com [209.85.220.199]) by kanga.kvack.org (Postfix) with ESMTP id A70306B0038 for ; Sun, 30 Apr 2017 19:14:29 -0400 (EDT) Received: by mail-qk0-f199.google.com with SMTP id f23so23749847qkh.21 for ; Sun, 30 Apr 2017 16:14:29 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id 83si12702513qky.280.2017.04.30.16.14.28 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 30 Apr 2017 16:14:28 -0700 (PDT) Date: Sun, 30 Apr 2017 19:14:24 -0400 From: Jerome Glisse Subject: Re: [PATCH v2] mm, zone_device: replace {get, put}_zone_device_page() with a single reference Message-ID: <20170430231421.GA15163@redhat.com> References: <20170428063913.iz6xjcxblecofjlq@gmail.com> <149339998297.24933.1129582806028305912.stgit@dwillia2-desk3.amr.corp.intel.com> <1743017574.4309811.1493400875692.JavaMail.zimbra@redhat.com> <1579714997.4315035.1493402406629.JavaMail.zimbra@redhat.com> <1295710462.4327805.1493406971970.JavaMail.zimbra@redhat.com> <20170428193305.GA3912@redhat.com> <20170429101726.cdczojcjjupb7myy@node.shutemov.name> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20170429101726.cdczojcjjupb7myy@node.shutemov.name> Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" Cc: Dan Williams , Ingo Molnar , "linux-kernel@vger.kernel.org" , Linux MM , Ingo Molnar , Andrew Morton , Logan Gunthorpe , Kirill Shutemov On Sat, Apr 29, 2017 at 01:17:26PM +0300, Kirill A. Shutemov wrote: > On Fri, Apr 28, 2017 at 03:33:07PM -0400, Jerome Glisse wrote: > > On Fri, Apr 28, 2017 at 12:22:24PM -0700, Dan Williams wrote: > > > Are you sure about needing to hook the 2 -> 1 transition? Could we > > > change ZONE_DEVICE pages to not have an elevated reference count when > > > they are created so you can keep the HMM references out of the mm hot > > > path? > > > > 100% sure on that :) I need to callback into driver for 2->1 transition > > no way around that. If we change ZONE_DEVICE to not have an elevated > > reference count that you need to make a lot more change to mm so that > > ZONE_DEVICE is never use as fallback for memory allocation. Also need > > to make change to be sure that ZONE_DEVICE page never endup in one of > > the path that try to put them back on lru. There is a lot of place that > > would need to be updated and it would be highly intrusive and add a > > lot of special cases to other hot code path. > > Could you explain more on where the requirement comes from or point me to > where I can read about this. > HMM ZONE_DEVICE pages are use like other pages (anonymous or file back page) in _any_ vma. So i need to know when a page is freed ie either as result of unmap, exit or migration or anything that would free the memory. For zone device a page is free once its refcount reach 1 so i need to catch refcount transition from 2->1 This is the only way i can inform the device that the page is now free. See https://cgit.freedesktop.org/~glisse/linux/commit/?h=hmm-v21&id=52da8fe1a088b87b5321319add79e43b8372ed7d There is _no_ way around that. Cheers, Jerome -- 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