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[ Upstream commit 8ba3c9d1c6d75d1e6af2087278b30e17f68e1fff ] If there was any event available on the TCP socket, tcp_poll() will be called to retrieve all the events. In tcp_poll(), we call sk_stream_is_writeable() which returns true as long as we are at least one byte below notsent_lowat. This will result in quite a few spurious EPLLOUT and frequent tiny sendmsg() calls as a result. Similar to sk_stream_write_space(), use __sk_stream_is_writeable with a wake value of 1, so that we set EPOLLOUT only if half the space is available for write. Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Sasha Levin <sashal@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.