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We use tun_alloc_skb() which calls sock_alloc_send_pskb() to allocate skb in the past. This socket based method is not suitable for high speed userspace like virtualization which usually: - ignore sk_sndbuf (INT_MAX) and expect to receive the packet as fast as possible - don't want to be block at sendmsg() To eliminate the above overheads, this patch tries to use build_skb() for small packet. We will do this only when the following conditions are all met: - TAP instead of TUN - sk_sndbuf is INT_MAX - caller don't want to be blocked - zerocopy is not used - packet size is smaller enough to use build_skb() Pktgen from guest to host shows ~11% improvement for rx pps of tap: Before: ~1.70Mpps After : ~1.88Mpps What's more important, this makes it possible to implement XDP for tap before creating skbs. Signed-off-by: Jason Wang <jasowang@redhat.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.