On 29/03/2020 20.47, Chaitanya Kulkarni wrote:
Hi, This patch-series is based on the original RFC patch series:- https://www.spinics.net/lists/linux-block/msg47933.html. I've designed a rough testcase based on the information present in the mailing list archive for original RFC, it may need some corrections from the author. If anyone is interested, test results are at the end of this patch. Following is the original cover-letter :- Information about continuous extent placement may be useful for some block devices. Say, distributed network filesystems, which provide block device interface, may use this information for better blocks placement over the nodes in their cluster, and for better performance. Block devices, which map a file on another filesystem (loop), may request the same length extent on underlining filesystem for less fragmentation and for batching allocation requests. Also, hypervisors like QEMU may use this information for optimization of cluster allocations. This patchset introduces REQ_OP_ASSIGN_RANGE, which is going to be used for forwarding user's fallocate(0) requests into block device internals. It rather similar to existing REQ_OP_DISCARD, REQ_OP_WRITE_ZEROES, etc. The corresponding exported primitive is called blkdev_issue_assign_range().
What exact semantics of that? It may/must preserve present data or may/must discard them, or may fill range with random garbage? Obviously I prefer weakest one - may discard data, may return garbage, may do nothing. I.e. lower layer could reuse blocks without zeroing, for encrypted storage this is even safe. So, this works as third type of dicasrd in addtion to REQ_OP_DISCARD and REQ_OP_SECURE_ERASE.
See [1/3] for the details. Patch [2/3] teaches loop driver to handle REQ_OP_ASSIGN_RANGE requests by calling fallocate(0). Patch [3/3] makes ext4 to notify a block device about fallocate(0). Here is a simple test I did: https://gist.github.com/tkhai/5b788651cdb74c1dbff3500745878856 I attached a file on ext4 to loop. Then, created ext4 partition on loop device and started the test in the partition. Direct-io is enabled on loop. The test fallocates 4G file and writes from some offset with given step, then it chooses another offset and repeats. After the test all the blocks in the file become written. The results shows that batching extents-assigning requests improves the performance: Before patchset: real ~ 1min 27sec After patchset: real ~ 1min 16sec (18% better) Ordinary fallocate() before writes improves the performance by batching the requests. These results just show, the same is in case of forwarding extents information to underlining filesystem. Regards, Chaitanya Changes from RFC:- 1. Add missing plumbing for REQ_OP_ASSIGN_RANGE similar to write-zeores. 2. Add a prep patch to create a helper to submit payloadless bios. 3. Design a testcases around the description present in the cover-letter. Chaitanya Kulkarni (1): block: create payloadless issue bio helper Kirill Tkhai (3): block: Add support for REQ_OP_ASSIGN_RANGE loop: Forward REQ_OP_ASSIGN_RANGE into fallocate(0) ext4: Notify block device about alloc-assigned blk block/blk-core.c | 5 ++ block/blk-lib.c | 115 +++++++++++++++++++++++++++++++------- block/blk-merge.c | 21 +++++++ block/blk-settings.c | 19 +++++++ block/blk-zoned.c | 1 + block/bounce.c | 1 + drivers/block/loop.c | 5 ++ fs/ext4/ext4.h | 2 + fs/ext4/extents.c | 12 +++- include/linux/bio.h | 9 ++- include/linux/blk_types.h | 2 + include/linux/blkdev.h | 34 +++++++++++ 12 files changed, 201 insertions(+), 25 deletions(-) 1. Setup :- ----------- # git log --oneline -5 c64a4c781915 (HEAD -> req-op-assign-range) ext4: Notify block device about alloc-assigned blk 000cbc6720a4 loop: Forward REQ_OP_ASSIGN_RANGE into fallocate(0) 89ceed8cac80 block: Add support for REQ_OP_ASSIGN_RANGE a798743e87e7 block: create payloadless issue bio helper b53df2e7442c (tag: block-5.6-2020-03-13) block: Fix partition support for host aware zoned block devices # cat /proc/kallsyms | grep -i blkdev_issue_assign_range ffffffffa3264a80 T blkdev_issue_assign_range ffffffffa4027184 r __ksymtab_blkdev_issue_assign_range ffffffffa40524be r __kstrtabns_blkdev_issue_assign_range ffffffffa405a8eb r __kstrtab_blkdev_issue_assign_range 2. Test program, will be moved to blktest once code is upstream :- ----------------- #define _GNU_SOURCE #include <sys/types.h> #include <unistd.h> #include <stdlib.h> #include <stdio.h> #include <fcntl.h> #include <errno.h> #define BLOCK_SIZE 4096 #define STEP (BLOCK_SIZE * 16) #define SIZE (1024 * 1024 * 1024ULL) int main(int argc, char *argv[]) { int fd, step, ret = 0; unsigned long i; void *buf; if (posix_memalign(&buf, BLOCK_SIZE, SIZE)) { perror("alloc"); exit(1); } fd = open("/mnt/loop0/file.img", O_RDWR | O_CREAT | O_DIRECT); if (fd < 0) { perror("open"); exit(1); } if (ftruncate(fd, SIZE)) { perror("ftruncate"); exit(1); } ret = fallocate(fd, 0, 0, SIZE); if (ret) { perror("fallocate"); exit(1); } for (step = STEP - BLOCK_SIZE; step >= 0; step -= BLOCK_SIZE) { printf("step=%u\n", step); for (i = step; i < SIZE; i += STEP) { errno = 0; if (pwrite(fd, buf, BLOCK_SIZE, i) != BLOCK_SIZE) { perror("pwrite"); exit(1); } } if (fsync(fd)) { perror("fsync"); exit(1); } } return 0; } 3. Test script, will be moved to blktests once code is upstream :- ------------------------------------------------------------------ # cat req_op_assign_test.sh #!/bin/bash -x NULLB_FILE="/mnt/backend/data" NULLB_MNT="/mnt/backend" LOOP_MNT="/mnt/loop0" delete_loop() { umount ${LOOP_MNT} losetup -D sleep 3 } delete_nullb() { umount ${NULLB_MNT} echo 1 > config/nullb/nullb0/power rmdir config/nullb/nullb0 sleep 3 } unload_modules() { rmmod drivers/block/loop.ko rmmod fs/ext4/ext4.ko rmmod drivers/block/null_blk.ko lsmod | grep -e ext4 -e loop -e null_blk } unload() { delete_loop delete_nullb unload_modules } load_ext4() { make -j $(nproc) M=fs/ext4 modules local src=fs/ext4/ local dest=/lib/modules/`uname -r`/kernel/fs/ext4 \cp ${src}/ext4.ko ${dest}/ modprobe mbcache modprobe jbd2 sleep 1 insmod fs/ext4/ext4.ko sleep 1 } load_nullb() { local src=drivers/block/ local dest=/lib/modules/`uname -r`/kernel/drivers/block \cp ${src}/null_blk.ko ${dest}/ modprobe null_blk nr_devices=0 sleep 1 mkdir config/nullb/nullb0 tree config/nullb/nullb0 echo 1 > config/nullb/nullb0/memory_backed echo 512 > config/nullb/nullb0/blocksize # 20 GB echo 20480 > config/nullb/nullb0/size echo 1 > config/nullb/nullb0/power sleep 2 IDX=`cat config/nullb/nullb0/index` lsblk | grep null${IDX} sleep 1 mkfs.ext4 /dev/nullb0 mount /dev/nullb0 ${NULLB_MNT} sleep 1 mount | grep nullb # 10 GB dd if=/dev/zero of=${NULLB_FILE} count=2621440 bs=4096 } load_loop() { local src=drivers/block/ local dest=/lib/modules/`uname -r`/kernel/drivers/block \cp ${src}/loop.ko ${dest}/ insmod drivers/block/loop.ko max_loop=1 sleep 3 /root/util-linux/losetup --direct-io=off /dev/loop0 ${NULLB_FILE} sleep 3 /root/util-linux/losetup ls -l /dev/loop* dmesg -c mkfs.ext4 /dev/loop0 mount /dev/loop0 ${LOOP_MNT} mount | grep loop0 } load() { make -j $(nproc) M=drivers/block modules load_ext4 load_nullb load_loop sleep 1 sync sync sync } unload load time ./test 4. Test Results :- ------------------ # ./req_op_assign_test.sh + NULLB_FILE=/mnt/backend/data + NULLB_MNT=/mnt/backend + LOOP_MNT=/mnt/loop0 + unload + delete_loop + umount /mnt/loop0 + losetup -D + sleep 3 + delete_nullb + umount /mnt/backend + echo 1 + rmdir config/nullb/nullb0 + sleep 3 + unload_modules + rmmod drivers/block/loop.ko + rmmod fs/ext4/ext4.ko + rmmod drivers/block/null_blk.ko + lsmod + grep -e ext4 -e loop -e null_blk + load ++ nproc + make -j 32 M=drivers/block modules CC [M] drivers/block/loop.o MODPOST 11 modules CC [M] drivers/block/loop.mod.o LD [M] drivers/block/loop.ko + load_ext4 ++ nproc + make -j 32 M=fs/ext4 modules CC [M] fs/ext4/balloc.o CC [M] fs/ext4/bitmap.o CC [M] fs/ext4/block_validity.o CC [M] fs/ext4/dir.o CC [M] fs/ext4/ext4_jbd2.o CC [M] fs/ext4/extents.o CC [M] fs/ext4/extents_status.o CC [M] fs/ext4/file.o CC [M] fs/ext4/fsmap.o CC [M] fs/ext4/fsync.o CC [M] fs/ext4/hash.o CC [M] fs/ext4/ialloc.o CC [M] fs/ext4/indirect.o CC [M] fs/ext4/inline.o CC [M] fs/ext4/inode.o CC [M] fs/ext4/ioctl.o CC [M] fs/ext4/mballoc.o CC [M] fs/ext4/migrate.o CC [M] fs/ext4/mmp.o CC [M] fs/ext4/move_extent.o CC [M] fs/ext4/namei.o CC [M] fs/ext4/page-io.o CC [M] fs/ext4/readpage.o CC [M] fs/ext4/resize.o CC [M] fs/ext4/super.o CC [M] fs/ext4/symlink.o CC [M] fs/ext4/sysfs.o CC [M] fs/ext4/xattr.o CC [M] fs/ext4/xattr_trusted.o CC [M] fs/ext4/xattr_user.o CC [M] fs/ext4/acl.o CC [M] fs/ext4/xattr_security.o LD [M] fs/ext4/ext4.o MODPOST 1 modules LD [M] fs/ext4/ext4.ko + local src=fs/ext4/ ++ uname -r + local dest=/lib/modules/5.6.0-rc3lbk+/kernel/fs/ext4 + cp fs/ext4//ext4.ko /lib/modules/5.6.0-rc3lbk+/kernel/fs/ext4/ + modprobe mbcache + modprobe jbd2 + sleep 1 + insmod fs/ext4/ext4.ko + sleep 1 + load_nullb + local src=drivers/block/ ++ uname -r + local dest=/lib/modules/5.6.0-rc3lbk+/kernel/drivers/block + cp drivers/block//null_blk.ko /lib/modules/5.6.0-rc3lbk+/kernel/drivers/block/ + modprobe null_blk nr_devices=0 + sleep 1 + mkdir config/nullb/nullb0 + tree config/nullb/nullb0 config/nullb/nullb0 ├── badblocks ├── blocking ├── blocksize ├── cache_size ├── completion_nsec ├── discard ├── home_node ├── hw_queue_depth ├── index ├── irqmode ├── mbps ├── memory_backed ├── power ├── queue_mode ├── size ├── submit_queues ├── use_per_node_hctx ├── zoned ├── zone_nr_conv └── zone_size 0 directories, 20 files + echo 1 + echo 512 + echo 20480 + echo 1 + sleep 2 ++ cat config/nullb/nullb0/index + IDX=0 + lsblk + grep null0 + sleep 1 + mkfs.ext4 /dev/nullb0 mke2fs 1.42.9 (28-Dec-2013) Filesystem label= OS type: Linux Block size=4096 (log=2) Fragment size=4096 (log=2) Stride=0 blocks, Stripe width=0 blocks 1310720 inodes, 5242880 blocks 262144 blocks (5.00%) reserved for the super user First data block=0 Maximum filesystem blocks=2153775104 160 block groups 32768 blocks per group, 32768 fragments per group 8192 inodes per group Superblock backups stored on blocks: 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 4096000 Allocating group tables: done Writing inode tables: done Creating journal (32768 blocks): done Writing superblocks and filesystem accounting information: done + mount /dev/nullb0 /mnt/backend + sleep 1 + mount + grep nullb /dev/nullb0 on /mnt/backend type ext4 (rw,relatime,seclabel) + dd if=/dev/zero of=/mnt/backend/data count=2621440 bs=4096 2621440+0 records in 2621440+0 records out 10737418240 bytes (11 GB) copied, 27.4579 s, 391 MB/s + load_loop + local src=drivers/block/ ++ uname -r + local dest=/lib/modules/5.6.0-rc3lbk+/kernel/drivers/block + cp drivers/block//loop.ko /lib/modules/5.6.0-rc3lbk+/kernel/drivers/block/ + insmod drivers/block/loop.ko max_loop=1 + sleep 3 + /root/util-linux/losetup --direct-io=off /dev/loop0 /mnt/backend/data + sleep 3 + /root/util-linux/losetup NAME SIZELIMIT OFFSET AUTOCLEAR RO BACK-FILE DIO LOG-SEC /dev/loop0 0 0 0 0 /mnt/backend/data 0 512 + ls -l /dev/loop0 /dev/loop-control brw-rw----. 1 root disk 7, 0 Mar 29 10:28 /dev/loop0 crw-rw----. 1 root disk 10, 237 Mar 29 10:28 /dev/loop-control + dmesg -c [42963.967060] null_blk: module loaded [42968.419481] EXT4-fs (nullb0): mounted filesystem with ordered data mode. Opts: (null) [42996.928141] loop: module loaded + mkfs.ext4 /dev/loop0 mke2fs 1.42.9 (28-Dec-2013) Discarding device blocks: done Filesystem label= OS type: Linux Block size=4096 (log=2) Fragment size=4096 (log=2) Stride=0 blocks, Stripe width=0 blocks 655360 inodes, 2621440 blocks 131072 blocks (5.00%) reserved for the super user First data block=0 Maximum filesystem blocks=2151677952 80 block groups 32768 blocks per group, 32768 fragments per group 8192 inodes per group Superblock backups stored on blocks: 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632 Allocating group tables: done Writing inode tables: done Creating journal (32768 blocks): done Writing superblocks and filesystem accounting information: done + mount /dev/loop0 /mnt/loop0 + mount + grep loop0 /dev/loop0 on /mnt/loop0 type ext4 (rw,relatime,seclabel) + sleep 1 + sync + sync + sync + ./test step=61440 step=57344 step=53248 step=49152 step=45056 step=40960 step=36864 step=32768 step=28672 step=24576 step=20480 step=16384 step=12288 step=8192 step=4096 step=0 real 9m34.472s user 0m0.062s sys 0m5.783s
