On 31.08.2016 19:42, Eric Dumazet wrote: > From: Eric Dumazet <eduma...@google.com> > > A while back, Paolo and Hannes sent an RFC patch adding threaded-able > napi poll loop support : (https://patchwork.ozlabs.org/patch/620657/) > > The problem seems to be that softirqs are very aggressive and are often > handled by the current process, even if we are under stress and that > ksoftirqd was scheduled, so that innocent threads would have more chance > to make progress. > > This patch makes sure that if ksoftirq is running, we let it > perform the softirq work. > > Jonathan Corbet summarized the issue in https://lwn.net/Articles/687617/ > > Tested: > > - NIC receiving traffic handled by CPU 0 > - UDP receiver running on CPU 0, using a single UDP socket. > - Incoming flood of UDP packets targeting the UDP socket. > > Before the patch, the UDP receiver could almost never get cpu cycles and > could only receive ~2,000 packets per second. > > After the patch, cpu cycles are split 50/50 between user application and > ksoftirqd/0, and we can effectively read ~900,000 packets per second, > a huge improvement in DOS situation. (Note that more packets are now > dropped by the NIC itself, since the BH handlers get less cpu cycles to > drain RX ring buffer) > > Since the load runs in well identified threads context, an admin can > more easily tune process scheduling parameters if needed. > > Reported-by: Paolo Abeni <pab...@redhat.com> > Reported-by: Hannes Frederic Sowa <han...@stressinduktion.org> > Signed-off-by: Eric Dumazet <eduma...@google.com> > Cc: David Miller <da...@davemloft.net > Cc: Jesper Dangaard Brouer <jbro...@redhat.com> > Cc: Peter Zijlstra <pet...@infradead.org> > Cc: Rik van Riel <r...@redhat.com>
Acked-by: Hannes Frederic Sowa <han...@stressinduktion.org> Thanks, Hannes
