From: Andrey Konovalov <andreyk...@google.com> Date: Thu, 1 Dec 2016 10:34:40 +0100
> This patch changes tun.c to call netif_receive_skb instead of netif_rx > when a packet is received (if CONFIG_4KSTACKS is not enabled to avoid > stack exhaustion). The difference between the two is that netif_rx queues > the packet into the backlog, and netif_receive_skb proccesses the packet > in the current context. > > This patch is required for syzkaller [1] to collect coverage from packet > receive paths, when a packet being received through tun (syzkaller collects > coverage per process in the process context). > > As mentioned by Eric this change also speeds up tun/tap. As measured by > Peter it speeds up his closed-loop single-stream tap/OVS benchmark by > about 23%, from 700k packets/second to 867k packets/second. > > A similar patch was introduced back in 2010 [2, 3], but the author found > out that the patch doesn't help with the task he had in mind (for cgroups > to shape network traffic based on the original process) and decided not to > go further with it. The main concern back then was about possible stack > exhaustion with 4K stacks. > > [1] https://github.com/google/syzkaller > > [2] https://www.spinics.net/lists/netdev/thrd440.html#130570 > > [3] https://www.spinics.net/lists/netdev/msg130570.html > > Signed-off-by: Andrey Konovalov <andreyk...@google.com> > --- > > Changes since v1: > - incorporate Eric's note about speed improvements in commit description > - use netif_receive_skb CONFIG_4KSTACKS is not enabled Applied to net-next, thanks!
