From patchwork Wed Jan 22 17:44:05 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexander Duyck X-Patchwork-Id: 11346197 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 76989139A for ; Wed, 22 Jan 2020 17:44:11 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 392732465B for ; Wed, 22 Jan 2020 17:44:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="uNA30+po" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 392732465B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id CB4886B026F; Wed, 22 Jan 2020 12:44:08 -0500 (EST) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id C64F86B0270; Wed, 22 Jan 2020 12:44:08 -0500 (EST) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A68806B0271; Wed, 22 Jan 2020 12:44:08 -0500 (EST) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0003.hostedemail.com [216.40.44.3]) by kanga.kvack.org (Postfix) with ESMTP id 8D44F6B026F for ; Wed, 22 Jan 2020 12:44:08 -0500 (EST) Received: from smtpin14.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with SMTP id 366AE8248047 for ; Wed, 22 Jan 2020 17:44:08 +0000 (UTC) X-FDA: 76405993776.14.group23_6f3892bd9d24 X-Spam-Summary: 2,0,0,a6d3e65a422c61fe,d41d8cd98f00b204,alexander.duyck@gmail.com,:kvm@vger.kernel.org:mst@redhat.com:linux-kernel@vger.kernel.org:willy@infradead.org:mhocko@kernel.org::akpm@linux-foundation.org:mgorman@techsingularity.net:vbabka@suse.cz: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,RULES_HIT:41:152:355:379:960:965:966:968:973:988:989:1260:1277:1311:1313:1314:1345:1359:1431:1437:1515:1516:1518:1535:1542:1593:1594:1711:1730:1747:1777:1792:2194:2196:2198:2199:2200:2201:2393:2553:2559:2562:2693:2731:2898:3138:3139:3140:3141:3142:3355:3743:3865:3866:3867:3868:3870:3871:3872:3874:4117:4250:4321:4385:4390:4395:5007:6119:6261:6653:6742:7576:7903:7974:8660:9108:9413:10004:10400:11026:11232:11473:11658:11914:12043:120 48:12291 X-HE-Tag: group23_6f3892bd9d24 X-Filterd-Recvd-Size: 6398 Received: from mail-pj1-f66.google.com (mail-pj1-f66.google.com [209.85.216.66]) by imf19.hostedemail.com (Postfix) with ESMTP for ; Wed, 22 Jan 2020 17:44:07 +0000 (UTC) Received: by mail-pj1-f66.google.com with SMTP id r67so223305pjb.0 for ; Wed, 22 Jan 2020 09:44:07 -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=uNA30+pop5ay5PQZOkmCvdwkxVlF197KdGENwnZSXy9SH+h1DEa3tdssjCM/toX6k+ ZDvRbSI05HPgjzZDwDHvfFBnWjhclVKWi3dG5V3tol6+dcKbJMHmPiKo2OH08uF/oIwR RyjG1zO4VWKvHolkJgTYdk4E8IGy97XzYvnl1FvW8AB1Nyn9eRM8KKAnExeDsOQcUmrf qwwJ6ulmFx3oZx/U0EBvCmErmORiXPr1YX9odO8WyRLhV7wYofNo4VrNwa2miI28rs6+ GR922Hu5AOCZ90IIZ7eZ5zom3e/mpna7fh892lv/ukr/tRAlyKYxJTlmBcn1N+9IS6bD M6MA== 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=EIQGfX+TI+OzxLKG3kptwvqkX5NH4FYbDgqF3mqxkuuRjVmebHGtleV5PLSZDqVgQl NtB2jpIa2FeiZq6jOu+FdIIax7ph4zBYG9S0TwYcHVgcAECEVhaeQsVc7VY4HIMtk1jZ 2vLUVnhjjLp4ku85ioQIpP4NS6kgz/szSQ7Fr7giWBXGIOULlR/5F/11eeiKA6+Z80CS 5+mxpv7lJlbwajVMxwNTzsO+5ll9M327RzP+eP3xGSw1L/r57tXe9tZXjDfxifrH/22+ Ar+yknMP8Q4IF3VLt6eWjfca+8PPxhihwN8LZZgJ7TUYGxC0NjrDmPuYfdjAF8JKgNBs DZFQ== X-Gm-Message-State: APjAAAVcRfgdQUNV3skROyX2ZtZBBCPo9rK0AuRGALF7RRutdQs+jQeb ilCF8umVOfHzoZq3A7pJlfw= X-Google-Smtp-Source: APXvYqwXbAfNhIYJ71ZW1bp4sCDs7ml8R2cISx8dIJqBDPPikGM4/SCCgJg1Ypb2iA+kSx3TUBdISw== X-Received: by 2002:a17:90a:ba07:: with SMTP id s7mr4364419pjr.75.1579715046758; Wed, 22 Jan 2020 09:44:06 -0800 (PST) Received: from localhost.localdomain ([2001:470:b:9c3:9e5c:8eff:fe4f:f2d0]) by smtp.gmail.com with ESMTPSA id h126sm49009065pfe.19.2020.01.22.09.44.06 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 22 Jan 2020 09:44:06 -0800 (PST) Subject: [PATCH v16.1 9/9] mm/page_reporting: 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: Wed, 22 Jan 2020 09:44:05 -0800 Message-ID: <20200122174405.6142.73500.stgit@localhost.localdomain> In-Reply-To: <20200122173040.6142.39116.stgit@localhost.localdomain> References: <20200122173040.6142.39116.stgit@localhost.localdomain> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 +