From: David Ahern <dsah...@gmail.com> Date: Fri, 4 Aug 2017 11:11:40 -0600
> On 8/4/17 11:07 AM, Eric Dumazet wrote: >> On Fri, 2017-08-04 at 09:38 -0700, Shaohua Li wrote: >>> From: Shaohua Li <s...@fb.com> >>> >>> In a syn flooding test, the fib6_table rwlock is a significant >>> bottleneck. While converting the rwlock to rcu sounds straighforward, >>> but is very challenging if it's possible. A percpu spinlock (lglock has >>> been removed from kernel, so I added a simple implementation here) is >>> quite trival for this problem since updating the routing table is a rare >>> event. In my test, the server receives around 1.5 Mpps in syn flooding >>> test without the patch in a dual sockets and 56-CPU system. With the >>> patch, the server receives around 3.8Mpps, and perf report doesn't show >>> the locking issue. >>> >>> Of course the percpu lock isn't as good as rcu, so this isn't intended >>> to replace rcu, but this is much better than current readwrite lock. >>> Before we have a rcu implementation, this is a good temporary solution. >>> Plus, this is a trival change, there is nothing to prevent pursuing a >>> rcu implmentation. >>> >>> Cc: Wei Wang <wei...@google.com> >>> Cc: Eric Dumazet <eric.duma...@gmail.com> >>> Cc: Stephen Hemminger <step...@networkplumber.org> >>> Signed-off-by: Shaohua Li <s...@fb.com> >>> --- >> >> Wei has almost done the RCU conversion. >> >> This patch is probably coming too late. > > > +1 > > I'd rather see the RCU conversion than a move to per-cpu locks. Me too.
