On Fri, 06 Jan 2017 22:10:42 -0500 (EST) David Miller <da...@davemloft.net> wrote:
> BTW Eric, you asked about kmalloc() allocation, you were CC:'d in the > patch which did this :-) > > commit 9a99d4a50cb8ce516adf0f2436138d4c8e6e4535 > Author: Cong Wang <amw...@redhat.com> > Date: Sun Jun 2 15:00:52 2013 +0000 > > icmp: avoid allocating large struct on stack > > struct icmp_bxm is a large struct, reduce stack usage > by allocating it on heap. > > Cc: Eric Dumazet <eric.duma...@gmail.com> > Cc: Joe Perches <j...@perches.com> > Cc: David S. Miller <da...@davemloft.net> > Signed-off-by: Cong Wang <amw...@redhat.com> > Signed-off-by: David S. Miller <da...@davemloft.net> Did a quick revert, and tested again. It is not the major bottleneck, but we do save something. The major bottleneck is still the call to __ip_route_output_key_hash (invoked by icmp_route_lookup). Single flow improvement from 1719182 pps to 1783368 pps. - 64186 pps - (1/1783368-1/1719182)*10^9 = -20.93 nanosec * 4GHz approx = 20.93*4 = 83.72 cycles The optimal SLUB fast-path on this machine is 54 cycles(tsc) 13.557 ns, thus the saving is actually higher than expected. But low compared to avoiding the icmp_route_lookup. -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer
