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Guenter Roeck
f76581f9f1
Commitd61fcfa4bb("blk-throttle: choose a small throtl_slice for SSD") introduced device type specific throttle slices if BLK_DEV_THROTTLING_LOW was enabled. Commitbf20ab538c("blk-throttle: remove CONFIG_BLK_DEV_THROTTLING_LOW") removed support for BLK_DEV_THROTTLING_LOW, but left the device type specific throttle slices in place. This effectively changed throttling behavior on systems with SSD which now use a different and non-configurable slice time compared to non-SSD devices. Practical impact is that throughput tests with low configured throttle values (65536 bps) experience less than expected throughput on SSDs, presumably due to rounding errors associated with the small throttle slice time used for those devices. The same tests pass when setting the throttle values to 65536 * 4 = 262144 bps. The original code sets the throttle slice time to DFL_THROTL_SLICE_HD if CONFIG_BLK_DEV_THROTTLING_LOW is disabled. Restore that code to fix the problem. With that, DFL_THROTL_SLICE_SSD is no longer necessary. Revert to the original code and re-introduce DFL_THROTL_SLICE to replace both DFL_THROTL_SLICE_HD and DFL_THROTL_SLICE_SSD. This effectively reverts commitd61fcfa4bb("blk-throttle: choose a small throtl_slice for SSD"). While at it, also remove MAX_THROTL_SLICE since it is not used anymore. Fixes:bf20ab538c("blk-throttle: remove CONFIG_BLK_DEV_THROTTLING_LOW") Cc: Yu Kuai <yukuai@kernel.org> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Khazhismel Kumykov <khazhy@google.com> Reviewed-by: Yu Kuai <yukuai@fnnas.com> 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 reStructuredText 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.