From patchwork Thu Dec 5 16:23:04 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexander Duyck X-Patchwork-Id: 11275179 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 42B6514BD for ; Thu, 5 Dec 2019 16:23:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 16AED24249 for ; Thu, 5 Dec 2019 16:23:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="ZsNkXEXz" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730069AbfLEQXJ (ORCPT ); Thu, 5 Dec 2019 11:23:09 -0500 Received: from mail-qv1-f68.google.com ([209.85.219.68]:45147 "EHLO mail-qv1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730055AbfLEQXJ (ORCPT ); Thu, 5 Dec 2019 11:23:09 -0500 Received: by mail-qv1-f68.google.com with SMTP id c2so1477580qvp.12; Thu, 05 Dec 2019 08:23:08 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:from:to:cc:date:message-id:in-reply-to:references :user-agent:mime-version:content-transfer-encoding; bh=d/px5ol/IpLIQI4VHOPlH6LMGgBauhkI55UKC6oSPnc=; b=ZsNkXEXzID1OTeSbGw/Kx3vdFdGzOrO8l5j9134wteIppk2pQIJoLnnIfvWa3qrolw Q19AiKvcxhHLQfsrjNSRQ/9Dls1la3DHIcx0TxCYc4dlI026GwSCIS8yIdgrh8LnHefh Oal98xdFl5LFD/ICNhGu8ewYrQdtshgRQCnyotfHjEypFCJi3sytxu4vYS9Luqeshs51 dBXvfFopLK7HEybFfYTZVqqby7KvjxdXrjMfx/b+Ag5KVK8VcUsEJnYM4ATDBYwWAhdT ZHz654EssUkrAMwJLN6pknPCgSh28TXqsDF4jAJc0PymSp7+4dk9+M7z4Y4F7jPCElsW z/Yg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:from:to:cc:date:message-id:in-reply-to :references:user-agent:mime-version:content-transfer-encoding; bh=d/px5ol/IpLIQI4VHOPlH6LMGgBauhkI55UKC6oSPnc=; b=hBhgFcQmtHHRWp3mjUOazuRjIso4VOR5o8ihheakCp45BwbvmpAtV1SQDQMsKYqq5A Mmq3k8e8ZCIk/ED6QYKexux6VCdd9N0lKaTIjHKvWMmz1xG17QEE6BULIMoc9SHzqwQ0 nDxakTMKkGBf23qpnCSEixbNri3U40d/Hqknx80X43x5kbE3+rFd2Y2lriZYJ9u2HZ9O vpJ2YO/4TM+w5Ju+UWLnn+r6jfmQrKu99ITXihbqGfRr6Oc9m9l4EAWhmfK1QxPQK9qT MfFX1rjJeS59snJiB2r7Np4Xvx1GqrJ0w0fVhedxWrhOUCpBABDHUohn2aG5BpnOLxqy xkLA== X-Gm-Message-State: APjAAAXBeZArMgOUkFFqACKVceL91EIz2yS6BCB4NwZf4Xtd/9yoW6Cx kvLn/SAucPQPC+SwHmHbpa4= X-Google-Smtp-Source: APXvYqyYiTP/iSYcxMoRgDysWgCYayNyROdgRBDPsb/IpTlb6ehCw3ju7P+6L8PufabVp5RjMx4Shw== X-Received: by 2002:a0c:b40d:: with SMTP id u13mr807826qve.54.1575562987657; Thu, 05 Dec 2019 08:23:07 -0800 (PST) Received: from localhost.localdomain ([2001:470:b:9c3:9e5c:8eff:fe4f:f2d0]) by smtp.gmail.com with ESMTPSA id g64sm4915241qke.43.2019.12.05.08.23.05 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 05 Dec 2019 08:23:07 -0800 (PST) Subject: [PATCH v15 7/7] mm: Add free page reporting documentation From: Alexander Duyck To: kvm@vger.kernel.org, mst@redhat.com, linux-kernel@vger.kernel.org, willy@infradead.org, mhocko@kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, mgorman@techsingularity.net, vbabka@suse.cz Cc: yang.zhang.wz@gmail.com, nitesh@redhat.com, konrad.wilk@oracle.com, david@redhat.com, pagupta@redhat.com, riel@surriel.com, lcapitulino@redhat.com, dave.hansen@intel.com, wei.w.wang@intel.com, aarcange@redhat.com, pbonzini@redhat.com, dan.j.williams@intel.com, alexander.h.duyck@linux.intel.com, osalvador@suse.de Date: Thu, 05 Dec 2019 08:23:04 -0800 Message-ID: <20191205162304.19548.33406.stgit@localhost.localdomain> In-Reply-To: <20191205161928.19548.41654.stgit@localhost.localdomain> References: <20191205161928.19548.41654.stgit@localhost.localdomain> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: Alexander Duyck Add documentation for free page reporting. Currently the only consumer is virtio-balloon, however it is possible that other drivers might make use of this so it is best to add a bit of documetation explaining at a high level how to use the API. Signed-off-by: Alexander Duyck --- Documentation/vm/free_page_reporting.rst | 41 ++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) create mode 100644 Documentation/vm/free_page_reporting.rst diff --git a/Documentation/vm/free_page_reporting.rst b/Documentation/vm/free_page_reporting.rst new file mode 100644 index 000000000000..33f54a450a4a --- /dev/null +++ b/Documentation/vm/free_page_reporting.rst @@ -0,0 +1,41 @@ +.. _free_page_reporting: + +===================== +Free Page Reporting +===================== + +Free page reporting is an API by which a device can register to receive +lists of pages that are currently unused by the system. This is useful in +the case of virtualization where a guest is then able to use this data to +notify the hypervisor that it is no longer using certain pages in memory. + +For the driver, typically a balloon driver, to use of this functionality +it will allocate and initialize a page_reporting_dev_info structure. The +field within the structure it will populate is the "report" function +pointer used to process the scatterlist. It must also guarantee that it can +handle at least PAGE_REPORTING_CAPACITY worth of scatterlist entries per +call to the function. A call to page_reporting_register will register the +page reporting interface with the reporting framework assuming no other +page reporting devices are already registered. + +Once registered the page reporting API will begin reporting batches of +pages to the driver. The API will start reporting pages 2 seconds after +the interface is registered and will continue to do so 2 seconds after any +page of a sufficiently high order is freed. + +Pages reported will be stored in the scatterlist passed to the reporting +function with the final entry having the end bit set in entry nent - 1. +While pages are being processed by the report function they will not be +accessible to the allocator. Once the report function has been completed +the pages will be returned to the free area from which they were obtained. + +Prior to removing a driver that is making use of free page reporting it +is necessary to call page_reporting_unregister to have the +page_reporting_dev_info structure that is currently in use by free page +reporting removed. Doing this will prevent further reports from being +issued via the interface. If another driver or the same driver is +registered it is possible for it to resume where the previous driver had +left off in terms of reporting free pages. + +Alexander Duyck, Dec 04, 2019 +