From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-f198.google.com (mail-qt0-f198.google.com [209.85.216.198]) by kanga.kvack.org (Postfix) with ESMTP id 88EDF6B0038 for ; Fri, 28 Apr 2017 14:00:14 -0400 (EDT) Received: by mail-qt0-f198.google.com with SMTP id u30so14928897qtu.14 for ; Fri, 28 Apr 2017 11:00:14 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id y129si6404437qke.157.2017.04.28.11.00.13 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 28 Apr 2017 11:00:13 -0700 (PDT) Date: Fri, 28 Apr 2017 14:00:06 -0400 (EDT) From: Jerome Glisse Message-ID: <1579714997.4315035.1493402406629.JavaMail.zimbra@redhat.com> In-Reply-To: References: <20170428063913.iz6xjcxblecofjlq@gmail.com> <149339998297.24933.1129582806028305912.stgit@dwillia2-desk3.amr.corp.intel.com> <1743017574.4309811.1493400875692.JavaMail.zimbra@redhat.com> Subject: Re: [PATCH v2] mm, zone_device: replace {get, put}_zone_device_page() with a single reference MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: Dan Williams Cc: Ingo Molnar , linux-kernel@vger.kernel.org, Linux MM , Ingo Molnar , Andrew Morton , Logan Gunthorpe , Kirill Shutemov > On Fri, Apr 28, 2017 at 10:34 AM, Jerome Glisse wrot= e: > >> Kirill points out that the calls to {get,put}_dev_pagemap() can be > >> removed from the mm fast path if we take a single get_dev_pagemap() > >> reference to signify that the page is alive and use the final put of t= he > >> page to drop that reference. > >> > >> This does require some care to make sure that any waits for the > >> percpu_ref to drop to zero occur *after* devm_memremap_page_release(), > >> since it now maintains its own elevated reference. > > > > This is NAK from HMM point of view as i need those call. So if you remo= ve > > them now i will need to add them back as part of HMM. >=20 > I thought you only need them at page free time? You can still hook > __put_page(). No, i need a hook when page refcount reach 1, not 0. That being said i don't care about put_dev_pagemap(page->pgmap); so that part of the patch is fine from HMM point of view but i definitly need to hook my- self in the general put_page() function. So i will have to undo part of this patch for HMM (put_page() will need to handle ZONE_DEVICE page differently). Cheers, J=C3=A9r=C3=B4me=20 -- 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