From e2462113b2003085ad16f15e1442ded64e2d9a29 Mon Sep 17 00:00:00 2001 From: Francesco Romani Date: Mon, 12 Jan 2015 14:11:13 +0100 Subject: block: add event when disk usage exceeds threshold Managing applications, like oVirt (http://www.ovirt.org), make extensive use of thin-provisioned disk images. To let the guest run smoothly and be not unnecessarily paused, oVirt sets a disk usage threshold (so called 'high water mark') based on the occupation of the device, and automatically extends the image once the threshold is reached or exceeded. In order to detect the crossing of the threshold, oVirt has no choice but aggressively polling the QEMU monitor using the query-blockstats command. This lead to unnecessary system load, and is made even worse under scale: deployments with hundreds of VMs are no longer rare. To fix this, this patch adds: * A new monitor command `block-set-write-threshold', to set a mark for a given block device. * A new event `BLOCK_WRITE_THRESHOLD', to report if a block device usage exceeds the threshold. * A new `write_threshold' field into the `BlockDeviceInfo' structure, to report the configured threshold. This will allow the managing application to use smarter and more efficient monitoring, greatly reducing the need of polling. [Updated qemu-iotests 067 output to add the new 'write_threshold' property. --Stefan] [Changed g_assert_false() to !g_assert() to fix the build on older glib versions. --Kevin] Signed-off-by: Francesco Romani Reviewed-by: Eric Blake Message-id: 1421068273-692-1-git-send-email-fromani@redhat.com Signed-off-by: Stefan Hajnoczi Signed-off-by: Kevin Wolf --- tests/qemu-iotests/067.out | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'tests/qemu-iotests/067.out') diff --git a/tests/qemu-iotests/067.out b/tests/qemu-iotests/067.out index 13ff3cd7aa..00b3eaefc7 100644 --- a/tests/qemu-iotests/067.out +++ b/tests/qemu-iotests/067.out @@ -43,6 +43,7 @@ Testing: -drive file=TEST_DIR/t.qcow2,format=qcow2,if=none,id=disk -device virti "drv": "qcow2", "iops": 0, "bps_wr": 0, + "write_threshold": 0, "encrypted": false, "bps": 0, "bps_rd": 0, @@ -218,6 +219,7 @@ Testing: -drive file=TEST_DIR/t.qcow2,format=qcow2,if=none,id=disk "drv": "qcow2", "iops": 0, "bps_wr": 0, + "write_threshold": 0, "encrypted": false, "bps": 0, "bps_rd": 0, @@ -423,6 +425,7 @@ Testing: "drv": "qcow2", "iops": 0, "bps_wr": 0, + "write_threshold": 0, "encrypted": false, "bps": 0, "bps_rd": 0, @@ -607,6 +610,7 @@ Testing: "drv": "qcow2", "iops": 0, "bps_wr": 0, + "write_threshold": 0, "encrypted": false, "bps": 0, "bps_rd": 0, @@ -717,6 +721,7 @@ Testing: "drv": "qcow2", "iops": 0, "bps_wr": 0, + "write_threshold": 0, "encrypted": false, "bps": 0, "bps_rd": 0, -- cgit v1.2.1