From patchwork Tue Feb 11 22:47:30 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexander Duyck X-Patchwork-Id: 11377061 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 337D614E3 for ; Tue, 11 Feb 2020 22:47:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0A20C20714 for ; Tue, 11 Feb 2020 22:47:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="vdsk1oZr" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727954AbgBKWri (ORCPT ); Tue, 11 Feb 2020 17:47:38 -0500 Received: from mail-wr1-f68.google.com ([209.85.221.68]:39848 "EHLO mail-wr1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727697AbgBKWri (ORCPT ); Tue, 11 Feb 2020 17:47:38 -0500 Received: by mail-wr1-f68.google.com with SMTP id y11so14614140wrt.6; Tue, 11 Feb 2020 14:47:37 -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=vdsk1oZrbgI3AQUQIbq7pQ1CHVFDsak9q0s76pRoLudWtUfRwf3J5HlnM6MZWEblNR cFnbL7sx4HzGtJYFOoOuzaZjjpXmxu2wCk567PVYA3vNpL9Ie7OHqpAcF+HO3DeJApGA sdLcAtiI1s+5tiXKsPIxagwX9ZFjbtzCd/fpIyD8DPXSt4xKxkOHgtkzMF05uuVjyvoU eVf+QjCIivhcJzD/zKdy4fLQq221jrgoPehukk81ne5FuQtHh4D1/FeX4b9m+vCnX/U0 iVZq89sxbasT+1oGo4ParZzn9jA7pn47H7d4uqAcS/epFwny88QESv06TPF7y8JIOA+O 69pA== 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=kpjnQf0xy5mN6+P85CfxuFSv09/ahiaJ5PmL+iiP0VQnqACIBfCba6npEN7HDZhaHU FH0Cl7N9J5yGkPLic0mS0nX8pVxTu6w0DkWA3uQfDjONmRcK9joYaDV47XqdDzprPOyY bwD2LMX+Ejs0isVx2pfIhZqNPFm8QLIlbaYGX6xGM08i85HchCiCc3PNzFHsUVf1nKzU FmCFUjTunED6eITnox1AxT3CjZxlHsc8ndR3zxZkVg+77TM5sL4YWJZ9jUoHAobNvo4a ex59nfUfIasxo75sBsB4qG1+VINkKDrDpx96mKF8x/MablKtQ2LySnlloI+jIyKboZiL R8TA== X-Gm-Message-State: APjAAAV91twkg/BrBPEDR9qP1v5CEIIxlNENC5dRLnxx+U6PefSr5Kwj Qa37CUxxNb+lhKmqcdwKpJc= X-Google-Smtp-Source: APXvYqxmTNJrmWKOa80PFKVIATMpGG5MV1aZHzg2Jd9nAr8x2mSvQKWTHDAHSjCH7L9I0U/0vHXAkA== X-Received: by 2002:a5d:6ac4:: with SMTP id u4mr10824067wrw.318.1581461256311; Tue, 11 Feb 2020 14:47:36 -0800 (PST) Received: from localhost.localdomain ([2001:470:b:9c3:9e5c:8eff:fe4f:f2d0]) by smtp.gmail.com with ESMTPSA id w19sm5366655wmc.22.2020.02.11.14.47.32 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 11 Feb 2020 14:47:35 -0800 (PST) Subject: [PATCH v17 9/9] mm/page_reporting: Add free page reporting documentation From: Alexander Duyck To: kvm@vger.kernel.org, david@redhat.com, mst@redhat.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, mgorman@techsingularity.net Cc: yang.zhang.wz@gmail.com, pagupta@redhat.com, konrad.wilk@oracle.com, nitesh@redhat.com, riel@surriel.com, willy@infradead.org, lcapitulino@redhat.com, dave.hansen@intel.com, wei.w.wang@intel.com, aarcange@redhat.com, pbonzini@redhat.com, dan.j.williams@intel.com, mhocko@kernel.org, alexander.h.duyck@linux.intel.com, vbabka@suse.cz, osalvador@suse.de Date: Tue, 11 Feb 2020 14:47:30 -0800 Message-ID: <20200211224730.29318.43815.stgit@localhost.localdomain> In-Reply-To: <20200211224416.29318.44077.stgit@localhost.localdomain> References: <20200211224416.29318.44077.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 +