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under udp flood the sk_receive_queue spinlock is heavily contended. This patch try to reduce the contention on such lock adding a second receive queue to the udp sockets; recvmsg() looks first in such queue and, only if empty, tries to fetch the data from sk_receive_queue. The latter is spliced into the newly added queue every time the receive path has to acquire the sk_receive_queue lock. The accounting of forward allocated memory is still protected with the sk_receive_queue lock, so udp_rmem_release() needs to acquire both locks when the forward deficit is flushed. On specific scenarios we can end up acquiring and releasing the sk_receive_queue lock multiple times; that will be covered by the next patch Suggested-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Paolo Abeni <pabeni@redhat.com> Acked-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.