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8dc932d3e8
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
----------------+--------+-------+-----------+-----------+--------
9011495c94 | R:256 | R:313 | R:276 | R:313 | R:323
(before faulty) | W:254 | W:253 | W:195 | W:204 | W:117
----------------+--------+-------+-----------+-----------+--------
5ff9f19231 | 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: 5ff9f19231 ("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>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.