diff options
| author | Peter Lieven <pl@kamp.de> | 2014-05-18 00:58:19 +0200 |
|---|---|---|
| committer | Kevin Wolf <kwolf@redhat.com> | 2014-05-19 13:42:27 +0200 |
| commit | 465bee1da82e43f18d10c43cc7566d0284ad13a9 (patch) | |
| tree | c98c26268e8f10a77bfc39abb72f72f8c7ac9ee8 /blockdev.c | |
| parent | 82a402e99f3f8c6177528ad6d561bf07ff6ee606 (diff) | |
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 <pl@kamp.de>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'blockdev.c')
| -rw-r--r-- | blockdev.c | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/blockdev.c b/blockdev.c index 78b927f045..1cbcc1c785 100644 --- a/blockdev.c +++ b/blockdev.c @@ -343,6 +343,7 @@ static DriveInfo *blockdev_init(const char *file, QDict *bs_opts, QemuOpts *opts; const char *id; bool has_driver_specific_opts; + BlockdevDetectZeroesOptions detect_zeroes; BlockDriver *drv = NULL; /* Check common options by copying from bs_opts to opts, all other options @@ -471,6 +472,24 @@ static DriveInfo *blockdev_init(const char *file, QDict *bs_opts, } } + detect_zeroes = + parse_enum_option(BlockdevDetectZeroesOptions_lookup, + qemu_opt_get(opts, "detect-zeroes"), + BLOCKDEV_DETECT_ZEROES_OPTIONS_MAX, + BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF, + &error); + if (error) { + error_propagate(errp, error); + goto early_err; + } + + if (detect_zeroes == BLOCKDEV_DETECT_ZEROES_OPTIONS_UNMAP && + !(bdrv_flags & BDRV_O_UNMAP)) { + error_setg(errp, "setting detect-zeroes to unmap is not allowed " + "without setting discard operation to unmap"); + goto early_err; + } + /* init */ dinfo = g_malloc0(sizeof(*dinfo)); dinfo->id = g_strdup(qemu_opts_id(opts)); @@ -481,6 +500,7 @@ static DriveInfo *blockdev_init(const char *file, QDict *bs_opts, } dinfo->bdrv->open_flags = snapshot ? BDRV_O_SNAPSHOT : 0; dinfo->bdrv->read_only = ro; + dinfo->bdrv->detect_zeroes = detect_zeroes; dinfo->refcount = 1; if (serial != NULL) { dinfo->serial = g_strdup(serial); @@ -2474,6 +2494,10 @@ QemuOptsList qemu_common_drive_opts = { .name = "copy-on-read", .type = QEMU_OPT_BOOL, .help = "copy read data from backing file into image file", + },{ + .name = "detect-zeroes", + .type = QEMU_OPT_STRING, + .help = "try to optimize zero writes (off, on, unmap)", }, { /* end of list */ } }, |