From: Maxim Mikityanskiy maxtram95@gmail.com
commit 8dc932d3e8afb65e12eba7495f046c83884c49bf upstream.
The cited commit introduced a serious regression with SATA write speed, as found by bisecting. This patch reverts this commit, which restores write speed back to the values observed before this commit.
The performance tests were done on a Helios4 NAS (2nd batch) with 4 HDDs (WD8003FFBX) using dd (bs=1M count=2000). "Direct" is a test with a single HDD, the rest are different RAID levels built over the first partitions of 4 HDDs. Test results are in MB/s, R is read, W is write.
| Direct | RAID0 | RAID10 f2 | RAID10 n2 | RAID6 ----------------+--------+-------+-----------+-----------+-------- 9011495c9466 | R:256 | R:313 | R:276 | R:313 | R:323 (before faulty) | W:254 | W:253 | W:195 | W:204 | W:117 ----------------+--------+-------+-----------+-----------+-------- 5ff9f19231a0 | R:257 | R:398 | R:312 | R:344 | R:391 (faulty commit) | W:154 | W:122 | W:67.7 | W:66.6 | W:67.2 ----------------+--------+-------+-----------+-----------+-------- 5.10.10 | R:256 | R:401 | R:312 | R:356 | R:375 unpatched | W:149 | W:123 | W:64 | W:64.1 | W:61.5 ----------------+--------+-------+-----------+-----------+-------- 5.10.10 | R:255 | R:396 | R:312 | R:340 | R:393 patched | W:247 | W:274 | W:220 | W:225 | W:121
Applying this patch doesn't hurt read performance, while improves the write speed by 1.5x - 3.5x (more impact on RAID tests). The write speed is restored back to the state before the faulty commit, and even a bit higher in RAID tests (which aren't HDD-bound on this device) - that is likely related to other optimizations done between the faulty commit and 5.10.10 which also improved the read speed.
Signed-off-by: Maxim Mikityanskiy maxtram95@gmail.com Fixes: 5ff9f19231a0 ("block: simplify set_init_blocksize") Cc: Christoph Hellwig hch@lst.de Cc: Jens Axboe axboe@kernel.dk Acked-by: Christoph Hellwig hch@lst.de Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/block_dev.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
--- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -134,7 +134,15 @@ EXPORT_SYMBOL(truncate_bdev_range);
static void set_init_blocksize(struct block_device *bdev) { - bdev->bd_inode->i_blkbits = blksize_bits(bdev_logical_block_size(bdev)); + unsigned int bsize = bdev_logical_block_size(bdev); + loff_t size = i_size_read(bdev->bd_inode); + + while (bsize < PAGE_SIZE) { + if (size & bsize) + break; + bsize <<= 1; + } + bdev->bd_inode->i_blkbits = blksize_bits(bsize); }
int set_blocksize(struct block_device *bdev, int size)