Hi all!
Here is a filter, which does preallocation on write.
In Virtuozzo we have to deal with some custom distributed storage
solution, where allocation is very-very expensive operation. We have to
workaround it in Qemu, so here is a new filter.
Still, the filter shows good results for me even for xfs and ext4.
Here are results, produced by new benchmark (last 4 patches):
All results are in iops (larger means better)
---------------------------------- ----------- -----------
A B
no-prealloc prealloc
ssd-ext4, aligned sequential 16k 19934±1.2% 27108±0.27%
A+36±2%
ssd-xfs, aligned sequential 16k 15528±5.5% 25953±3.3%
A+67±11%
hdd-ext4, aligned sequential 16k 5079±29% 3165±11%
A-38±36%
hdd-xfs, aligned sequential 16k 4096±95% 3321±7.6%
A-19±101%
ssd-ext4, unaligned sequential 64k 19969±1.9% 27043±0.49%
A+35±3%
ssd-xfs, unaligned sequential 64k 15403±2.8% 25725±6.4%
A+67±13%
hdd-ext4, unaligned sequential 64k 5250±17% 3239±8.7%
A-38±23%
hdd-xfs, unaligned sequential 64k 5291±8.2% 3336±4.2%
A-37±11%
---------------------------------- ----------- -----------
Note: it's on Fedora 30, kernel 5.6.13-100.fc30.x86_64
The tests are actually qemu-img bench, run like:
./qemu-img create -f qcow2 $img 16G
aligned:
./qemu-img bench -c 10000 -d 64 -f qcow2 -s 16k -t none -n -w $img
unaligned
./qemu-img bench -c 10000 -d 64 -f qcow2 -o 1k -s 64k -t none -n -w $img
and for preallocation, you'll drop -f qcow2, add --image-opts, and
instead of just $img use
driver=qcow2,file.driver=preallocate,file.file.driver=file,file.file.filename=$img
v6:
05: add Max's r-b
06: add Max's r-b
07: new
08: Changed a lot. really. no .active now, support more use-cases.
Somehow, now I see performance benefit on xfs too :)
probably due to .zero_start feature.
09: new
10: new
11: mostly rewritten, a lot more cases, drop r-b
12-15: new, to produce final benchmark table
Vladimir Sementsov-Ogievskiy (15):
block: simplify comment to BDRV_REQ_SERIALISING
block/io.c: drop assertion on double waiting for request serialisation
block/io: split out bdrv_find_conflicting_request
block/io: bdrv_wait_serialising_requests_locked: drop extra bs arg
block: bdrv_mark_request_serialising: split non-waiting function
block: introduce BDRV_REQ_NO_WAIT flag
block: bdrv_check_perm(): process children anyway
block: introduce preallocate filter
qemu-io: add preallocate mode parameter for truncate command
iotests: qemu_io_silent: support --image-opts
iotests: add 298 to test new preallocate filter driver
scripts/simplebench: support iops
scripts/simplebench: improve view of ascii table
scripts/simplebench: improve ascii table: add difference line
scripts/simplebench: add bench_prealloc.py
docs/system/qemu-block-drivers.rst.inc | 26 ++
qapi/block-core.json | 20 +-
include/block/block.h | 20 +-
include/block/block_int.h | 3 +-
block.c | 10 +-
block/file-posix.c | 2 +-
block/io.c | 130 +++---
block/preallocate.c | 556 +++++++++++++++++++++++++
qemu-io-cmds.c | 46 +-
block/meson.build | 1 +
scripts/simplebench/bench_prealloc.py | 128 ++++++
scripts/simplebench/simplebench.py | 103 ++++-
tests/qemu-iotests/298 | 186 +++++++++
tests/qemu-iotests/298.out | 5 +
tests/qemu-iotests/group | 1 +
tests/qemu-iotests/iotests.py | 7 +-
16 files changed, 1146 insertions(+), 98 deletions(-)
create mode 100644 block/preallocate.c
create mode 100755 scripts/simplebench/bench_prealloc.py
create mode 100644 tests/qemu-iotests/298
create mode 100644 tests/qemu-iotests/298.out
--
2.21.3