d0b2b70eb1
With the current implementation of the UFS driver active_queues is 1 instead of 0 if all UFS request queues are idle. That causes hctx_may_queue() to divide the queue depth by 2 when queueing a request and hence reduces the usable queue depth. The shared tag set code in the block layer keeps track of the number of active request queues. blk_mq_tag_busy() is called before a request is queued onto a hwq and blk_mq_tag_idle() is called some time after the hwq became idle. blk_mq_tag_idle() is called from inside blk_mq_timeout_work(). Hence, blk_mq_tag_idle() is only called if a timer is associated with each request that is submitted to a request queue that shares a tag set with another request queue. Adds a blk_mq_start_request() call in ufshcd_exec_dev_cmd(). This doubles the queue depth on my test setup from 16 to 32. In addition to increasing the usable queue depth, also fix the documentation of the 'timeout' parameter in the header above ufshcd_exec_dev_cmd(). Link: https://lore.kernel.org/r/20210513164912.5683-1-bvanassche@acm.org Fixes: 7252a3603015 ("scsi: ufs: Avoid busy-waiting by eliminating tag conflicts") Cc: Can Guo <cang@codeaurora.org> Cc: Alim Akhtar <alim.akhtar@samsung.com> Cc: Avri Altman <avri.altman@wdc.com> Cc: Stanley Chu <stanley.chu@mediatek.com> Cc: Bean Huo <beanhuo@micron.com> Cc: Adrian Hunter <adrian.hunter@intel.com> Reviewed-by: Can Guo <cang@codeaurora.org> Signed-off-by: Bart Van Assche <bvanassche@acm.org> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
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.