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2299ceec36
ublk_copy_user_pages()/ublk_copy_io_pages() currently uses iov_iter_get_pages2() to extract the pages from the iov_iter and memcpy()s between the bvec_iter and the iov_iter's pages one at a time. Switch to using copy_to_iter()/copy_from_iter() instead. This avoids the user page reference count increments and decrements and needing to split the memcpy() at user page boundaries. It also simplifies the code considerably. Ming reports a 40% throughput improvement when issuing I/O to the selftests null ublk server with zero-copy disabled. Signed-off-by: Caleb Sander Mateos <csander@purestorage.com> Reviewed-by: Ming Lei <ming.lei@redhat.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.