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While running a single stream UDPv6 test, we observed that amount of CPU spent in NET_RX softirq was much greater than UDPv4 for an equivalent receive rate. The test here was run on an ARM64 based Android system. On further analysis with perf, we found that UDPv6 was spending significant time in the statistics netfilter targets which did socket lookup per packet. These statistics rules perform a lookup when there is no socket associated with the skb. Since there are multiple instances of these rules based on UID, there will be equal number of lookups per skb. By introducing early demux for UDPv6, we avoid the redundant lookups. This also helped to improve the performance (800Mbps -> 870Mbps) on a CPU limited system in a single stream UDPv6 receive test with 1450 byte sized datagrams using iperf. v1->v2: Use IPv6 cookie to validate dst instead of 0 as suggested by Eric Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org> 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.