40510a639e
Currently, queue io_cpu assignment is done sequentially for default, read and poll queues based on queue id. This causes miss-alignment between context of CPU initiating I/O and the I/O worker thread processing queued requests or completions. Change to modify queue io_cpu assignment to take into account queue maps offset. Each queue io_cpu will start at zero for each queue map. This essentially aligns read/poll queues to start over the same range as default queues. Testing performed by Mark with: - ram device (nvmet) - single CPU core (pinned) - 100% 4k reads - engine io_uring (not using sq_thread option) - hipri flag set Micro-benchmark results show a net gain of: - increase of 18%-29% in IOPs - reduction of 16%-22% in average latency - reduction of 7%-23% in 99.99% latency Baseline: ======== QDepth/Batch | IOPs [k] | Avg. Lat [us] | 99.99% Lat [us] ----------------------------------------------------------------- 1/1 | 32.4 | 30.11 | 50.94 32/8 | 179 | 168.20 | 371 CPU alignment: ============= QDepth/Batch | IOPs [k] | Avg. Lat [us] | 99.99% Lat [us] ----------------------------------------------------------------- 1/1 | 38.5 | 25.18 | 39.16 32/8 | 231 | 130.75 | 343 Reported-by: Mark Wunderlich <mark.wunderlich@intel.com> Signed-off-by: Sagi Grimberg <sagi@grimberg.me> Signed-off-by: Keith Busch <kbusch@kernel.org>
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.