33946518d4
This patchset is intended to reduce the number of extra system calls imposed by TCP receive zerocopy. For ping-pong RPC style workloads, this patchset has demonstrated a system call reduction of about 30% when coupled with userspace changes. For applications using epoll, returning sk_err along with the result of tcp receive zerocopy could remove the need to call recvmsg()=-EAGAIN after a spurious wakeup. Consider a multi-threaded application using epoll. A thread may awaken with EPOLLIN but another thread may already be reading. The spuriously-awoken thread does not necessarily know that another thread 'won'; rather, it may be possible that it was woken up due to the presence of an error if there is no data. A zerocopy read receiving 0 bytes thus would need to be followed up by recvmsg to be sure. Instead, we return sk_err directly with zerocopy, so the application can avoid this extra system call. Signed-off-by: Arjun Roy <arjunroy@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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.