From patchwork Fri Jan 25 14:14:35 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Luiz Capitulino X-Patchwork-Id: 215741 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 5B5AA2C0090 for ; Sat, 26 Jan 2013 01:15:40 +1100 (EST) Received: from localhost ([::1]:33731 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Tyk4A-0001mB-Bl for incoming@patchwork.ozlabs.org; Fri, 25 Jan 2013 09:15:38 -0500 Received: from eggs.gnu.org ([208.118.235.92]:34917) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Tyk3J-0000Nb-Id for qemu-devel@nongnu.org; Fri, 25 Jan 2013 09:14:52 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Tyk3C-0004ZD-7C for qemu-devel@nongnu.org; Fri, 25 Jan 2013 09:14:45 -0500 Received: from mx1.redhat.com ([209.132.183.28]:11252) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Tyk3C-0004Z8-0K for qemu-devel@nongnu.org; Fri, 25 Jan 2013 09:14:38 -0500 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r0PEEbaf028944 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Fri, 25 Jan 2013 09:14:37 -0500 Received: from localhost (ovpn-113-104.phx2.redhat.com [10.3.113.104]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id r0PEEamY027760; Fri, 25 Jan 2013 09:14:37 -0500 From: Luiz Capitulino To: qemu-devel@nongnu.org Date: Fri, 25 Jan 2013 12:14:35 -0200 Message-Id: <1359123278-8681-5-git-send-email-lcapitulino@redhat.com> In-Reply-To: <1359123278-8681-1-git-send-email-lcapitulino@redhat.com> References: <1359123278-8681-1-git-send-email-lcapitulino@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.23 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: aliguori@us.ibm.com Subject: [Qemu-devel] [PULL 4/7] docs: document virtio-balloon stats X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Signed-off-by: Luiz Capitulino Reviewed-by: Eric Blake --- docs/virtio-balloon-stats.txt | 104 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 104 insertions(+) create mode 100644 docs/virtio-balloon-stats.txt diff --git a/docs/virtio-balloon-stats.txt b/docs/virtio-balloon-stats.txt new file mode 100644 index 0000000..f74612f --- /dev/null +++ b/docs/virtio-balloon-stats.txt @@ -0,0 +1,104 @@ +virtio balloon memory statistics +================================ + +The virtio balloon driver supports guest memory statistics reporting. These +statistics are available to QEMU users as QOM (QEMU Object Model) device +properties via a polling mechanism. + +Before querying the available stats, clients first have to enable polling. +This is done by writing a time interval value (in seconds) to the +guest-stats-polling-interval property. This value can be: + + > 0 enables polling in the specified interval. If polling is already + enabled, the polling time interval is changed to the new value + + 0 disables polling. Previous polled statistics are still valid and + can be queried. + +Once polling is enabled, the virtio-balloon device in QEMU will start +polling the guest's balloon driver for new stats in the specified time +interval. + +To retrieve those stats, clients have to query the guest-stats property, +which will return a dictionary containing: + + o A key named 'stats', containing all available stats. If the guest + doesn't support a particular stat, or if it couldn't be retrieved, + its value will be -1. Currently, the following stats are supported: + + - stat-swap-in + - stat-swap-out + - stat-major-faults + - stat-minor-faults + - stat-free-memory + - stat-total-memory + + o A key named last-update, which contains the last stats update + timestamp in seconds. Since this timestamp is generated by the host, + a buggy guest can't influence its value + +It's also important to note the following: + + - Previously polled statistics remain available even if the polling is + later disabled + + - As noted above, if a guest doesn't support a particular stat its value + will always be -1. However, it's also possible that a guest temporarily + couldn't update one or even all stats. If this happens, just wait for + the next update + + - Polling can be enabled even if the guest doesn't have stats support + or the balloon driver wasn't loaded in the guest. If this is the case + and stats are queried, an error will be returned + + - The polling timer is only re-armed when the guest responds to the + statistics request. This means that if a (buggy) guest doesn't ever + respond to the request the timer will never be re-armed, which has + the same effect as disabling polling + +Here are a few examples. QEMU is started with '-balloon virtio', which +generates '/machine/peripheral-anon/device[1]' as the QOM path for the +balloon device. + +Enable polling with 2 seconds interval: + +{ "execute": "qom-set", + "arguments": { "path": "/machine/peripheral-anon/device[1]", + "property": "guest-stats-polling-interval", "value": 2 } } + +{ "return": {} } + +Change polling to 10 seconds: + +{ "execute": "qom-set", + "arguments": { "path": "/machine/peripheral-anon/device[1]", + "property": "guest-stats-polling-interval", "value": 10 } } + +{ "return": {} } + +Get stats: + +{ "execute": "qom-get", + "arguments": { "path": "/machine/peripheral-anon/device[1]", + "property": "guest-stats" } } +{ + "return": { + "stats": { + "stat-swap-out": 0, + "stat-free-memory": 844943360, + "stat-minor-faults": 219028, + "stat-major-faults": 235, + "stat-total-memory": 1044406272, + "stat-swap-in": 0 + }, + "last-update": 1358529861 + } +} + +Disable polling: + +{ "execute": "qom-set", + "arguments": { "path": "/machine/peripheral-anon/device[1]", + "property": "stats-polling-interval", "value": 0 } } + +{ "return": {} }