8af870aa5b
bdev based polled O_DIRECT is currently quite a bit faster than passthru on the same device, and one of the reaons is that we're not able to use the bio caching for passthru IO. If REQ_POLLED is set on the request, use the fs bio set for grabbing a bio from the caches, if available. This saves 5-6% of CPU over head for polled passthru IO. Reviewed-by: Chaitanya Kulkarni <kch@nvidia.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 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.