a9a7e30fd9
This memset in the fast path costs a lot of cycles on my setup. Here's a
top-of-profile of doing ~6.7M IOPS:
+ 5.90% io_uring [nvme] [k] nvme_queue_rq
+ 5.32% io_uring [nvme_core] [k] nvme_setup_cmd
+ 5.17% io_uring [kernel.vmlinux] [k] io_submit_sqes
+ 4.97% io_uring [kernel.vmlinux] [k] blkdev_direct_IO
and a perf diff with this patch:
0.92% +4.40% [nvme_core] [k] nvme_setup_cmd
reducing it from 5.3% to only 0.9%. This takes it from the 2nd most
cycle consumer to something that's mostly irrelevant.
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Keith Busch <kbusch@kernel.org>
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.