From 465bee1da82e43f18d10c43cc7566d0284ad13a9 Mon Sep 17 00:00:00 2001 From: Peter Lieven Date: Sun, 18 May 2014 00:58:19 +0200 Subject: block: optimize zero writes with bdrv_write_zeroes this patch tries to optimize zero write requests by automatically using bdrv_write_zeroes if it is supported by the format. This significantly speeds up file system initialization and should speed zero write test used to test backend storage performance. I ran the following 2 tests on my internal SSD with a 50G QCOW2 container and on an attached iSCSI storage. a) mkfs.ext4 -E lazy_itable_init=0,lazy_journal_init=0 /dev/vdX QCOW2 [off] [on] [unmap] ----- runtime: 14secs 1.1secs 1.1secs filesize: 937M 18M 18M iSCSI [off] [on] [unmap] ---- runtime: 9.3s 0.9s 0.9s b) dd if=/dev/zero of=/dev/vdX bs=1M oflag=direct QCOW2 [off] [on] [unmap] ----- runtime: 246secs 18secs 18secs filesize: 51G 192K 192K throughput: 203M/s 2.3G/s 2.3G/s iSCSI* [off] [on] [unmap] ---- runtime: 8mins 45secs 33secs throughput: 106M/s 1.2G/s 1.6G/s allocated: 100% 100% 0% * The storage was connected via an 1Gbit interface. It seems to internally handle writing zeroes via WRITESAME16 very fast. Signed-off-by: Peter Lieven Signed-off-by: Kevin Wolf --- hmp.c | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'hmp.c') diff --git a/hmp.c b/hmp.c index 5c4d612..ff506f3 100644 --- a/hmp.c +++ b/hmp.c @@ -341,6 +341,11 @@ void hmp_info_block(Monitor *mon, const QDict *qdict) info->value->inserted->backing_file_depth); } + if (info->value->inserted->detect_zeroes != BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF) { + monitor_printf(mon, " Detect zeroes: %s\n", + BlockdevDetectZeroesOptions_lookup[info->value->inserted->detect_zeroes]); + } + if (info->value->inserted->bps || info->value->inserted->bps_rd || info->value->inserted->bps_wr -- cgit v1.1