On Wed, Jun 12, 2019 at 12:52 PM Eric Dumazet <eduma...@google.com> wrote: > > Using tcpdump (or other af_packet user) on a busy host can lead to > catastrophic consequences, because suddenly, potentially all cpus > are spinning on a contended spinlock. > > Both packet_rcv() and tpacket_rcv() grab the spinlock > to eventually find there is no room for an additional packet. > > This patch series align packet_rcv() and tpacket_rcv() to both > check if the queue is full before grabbing the spinlock. > > If the queue is full, they both increment a new atomic counter > placed on a separate cache line to let readers drain the queue faster. > > There is still false sharing on this new atomic counter, > we might in the future make it per cpu if there is interest. > > Eric Dumazet (8): > net/packet: constify __packet_get_status() argument > net/packet: constify packet_lookup_frame() and __tpacket_has_room() > net/packet: constify prb_lookup_block() and __tpacket_v3_has_room() > net/packet: constify __packet_rcv_has_room() > net/packet: make tp_drops atomic > net/packet: implement shortcut in tpacket_rcv() > net/packet: remove locking from packet_rcv_has_room() > net/packet: introduce packet_rcv_try_clear_pressure() helper > > net/packet/af_packet.c | 96 ++++++++++++++++++++++++-----------
For the series: Acked-by: Willem de Bruijn <will...@google.com> Thanks Eric
