ping. Finally, what about this? 07.08.2018 20:43, Vladimir Sementsov-Ogievskiy wrote:
Hi all!Here is an asynchronous scheme for handling fragmented qcow2 reads and writes. Both qcow2 read and write functions loops through sequential portions of data. The series aim it to parallelize these loops iterations. It improves performance for fragmented qcow2 images, I've tested it as follows: I have four 4G qcow2 images (with default 64k block size) on my ssd disk: t-seq.qcow2 - sequentially written qcow2 image t-reverse.qcow2 - filled by writing 64k portions from end to the start t-rand.qcow2 - filled by writing 64k portions (aligned) in random order t-part-rand.qcow2 - filled by shuffling order of 64k writes in 1m clusters (see source code of image generation in the end for details) and the test (sequential io by 1mb chunks): test write: for t in /ssd/t-*; \ do sync; echo 1 > /proc/sys/vm/drop_caches; echo === $t ===; \ ./qemu-img bench -c 4096 -d 1 -f qcow2 -n -s 1m -t none -w $t; \ done test read (same, just drop -w parameter): for t in /ssd/t-*; \ do sync; echo 1 > /proc/sys/vm/drop_caches; echo === $t ===; \ ./qemu-img bench -c 4096 -d 1 -f qcow2 -n -s 1m -t none $t; \ done short info about parameters: -w - do writes (otherwise do reads) -c - count of blocks -s - block size -t none - disable cache -n - native aio -d 1 - don't use parallel requests provided by qemu-img bench itself results: +-----------+-----------+----------+-----------+----------+ | file | wr before | wr after | rd before | rd after | +-----------+-----------+----------+-----------+----------+ | seq | 8.605 | 8.636 | 9.043 | 9.010 | | reverse | 9.934 | 8.654 | 17.162 | 8.662 | | rand | 9.983 | 8.687 | 19.775 | 9.010 | | part-rand | 9.871 | 8.650 | 14.241 | 8.669 | +-----------+-----------+----------+-----------+----------+ Performance gain is obvious, especially for read. how images are generated: === gen-writes file === #!/usr/bin/env python import random import sys size = 4 * 1024 * 1024 * 1024 block = 64 * 1024 block2 = 1024 * 1024 arg = sys.argv[1] if arg in ('rand', 'reverse', 'seq'): writes = list(range(0, size, block)) if arg == 'rand': random.shuffle(writes) elif arg == 'reverse': writes.reverse() elif arg == 'part-rand': writes = [] for off in range(0, size, block2): wr = list(range(off, off + block2, block)) random.shuffle(wr) writes.extend(wr) elif arg != 'seq': sys.exit(1) for w in writes: print 'write -P 0xff {} {}'.format(w, block) print 'q' === gen-test-images.sh file === #!/bin/bash IMG_PATH=/ssd for name in seq reverse rand part-rand; do IMG=$IMG_PATH/t-$name.qcow2 echo createing $IMG ... rm -f $IMG qemu-img create -f qcow2 $IMG 4G gen-writes $name | qemu-io $IMG done Denis V. Lunev (1): qcow2: move qemu_co_mutex_lock below decryption procedure Vladimir Sementsov-Ogievskiy (6): qcow2: bdrv_co_pwritev: move encryption code out of lock qcow2: split out reading normal clusters from qcow2_co_preadv qcow2: async scheme for qcow2_co_preadv qcow2: refactor qcow2_co_pwritev: split out qcow2_co_do_pwritev qcow2: refactor qcow2_co_pwritev locals scope qcow2: async scheme for qcow2_co_pwritev block/qcow2.c | 506 +++++++++++++++++++++++++++++-------- tests/qemu-iotests/026.out | 18 +- tests/qemu-iotests/026.out.nocache | 20 +- 3 files changed, 415 insertions(+), 129 deletions(-)
-- Best regards, Vladimir
