From patchwork Fri Jan 3 21:17:10 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexander Duyck X-Patchwork-Id: 11317435 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 B25A513A4 for ; Fri, 3 Jan 2020 21:17:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 85FD6206DB for ; Fri, 3 Jan 2020 21:17:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Hprox+7Y" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728882AbgACVRM (ORCPT ); Fri, 3 Jan 2020 16:17:12 -0500 Received: from mail-pf1-f195.google.com ([209.85.210.195]:37160 "EHLO mail-pf1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728872AbgACVRL (ORCPT ); Fri, 3 Jan 2020 16:17:11 -0500 Received: by mail-pf1-f195.google.com with SMTP id p14so24034220pfn.4; Fri, 03 Jan 2020 13:17:11 -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=Hprox+7YhX4vp/7ApJs7XtJYtsa0BYDFC2QN81cfX/asePRHFYKBPlY/F5X2RsAV3i 58FRXPyIAH9AT4MIcQQ179PjkaUhX4tTRtL73lMOcEeWsjK9cGvMxVD/VVamyj3VGsw3 TV+ZUAK5eon63Er2i4SNqwkx9bTYiCRGvlQAIEotBkzRTlDX9gSCxKXUHSBj37tbwzer Oe2xqBTKi3KRGPr1wf1921IvBivfrygOzuNn9KMsRYtIDEDcXzxMxQtHBV0LHfGTZteR Ix64ynkVRsPzzNrwlOOIXl/uBgXZyyWStGYkbrJdk7nLpXuPPIjrTXCFYta6oFLnCJug cAMA== 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=atSjubplmkHVrO7BVa2mrsxmhG1AQYfwLYU4+9C2F72QqvK6kKDUa9GAjUnOBttK1Y X7tcRWbiPyGPiPLCMFzHP2JkTLlk3NTHiScKiCl50GDeeGcszemQzRByMBMxqmmRcCDG 73aBV0i3P24UYp7csWyWL5ezBtbocrPYeo23B9GdKZ9eLM33tRuVLzC15y7Y3HUgMPDP SkccIG8qTa99TMHHnC3rulfywnc2NDbbMEbtwYYNP6YUFzeK6Mq+1tjqHXp19qoll+fL wNDtVWKW72vDUJI6wDOo6f8vsKnWSgcPs4JAv2HfOqh+oy6kElDQAN8FvGHAeeKY706q p8cg== X-Gm-Message-State: APjAAAWXrU3JVBON7se+9xCS0yE/VHY/I1UUULiQdD+QvfjOOre37Tlp BkIzZmc4iVDeskSc4Q5jftKg7ZC/T6s= X-Google-Smtp-Source: APXvYqyY3fKbNPGAiS+tAsYD6rrQUojk2xvXkRF2/sBCy3c3WSTOc4Rf9CnsNPVEbSYT6rLPnfMDAg== X-Received: by 2002:a63:444c:: with SMTP id t12mr95445975pgk.433.1578086230990; Fri, 03 Jan 2020 13:17:10 -0800 (PST) Received: from localhost.localdomain ([2001:470:b:9c3:9e5c:8eff:fe4f:f2d0]) by smtp.gmail.com with ESMTPSA id u23sm68481143pfm.29.2020.01.03.13.17.10 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 03 Jan 2020 13:17:10 -0800 (PST) Subject: [PATCH v16 9/9] 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: Fri, 03 Jan 2020 13:17:10 -0800 Message-ID: <20200103211709.29237.75092.stgit@localhost.localdomain> In-Reply-To: <20200103210509.29237.18426.stgit@localhost.localdomain> References: <20200103210509.29237.18426.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 +