From: Eric Dumazet <eric.duma...@gmail.com> Date: Sun, 01 May 2016 16:47:26 -0700
> From: Eric Dumazet <eduma...@google.com> > > In presence of inelastic flows and stress, we can call > fq_codel_drop() for every packet entering fq_codel qdisc. > > fq_codel_drop() is quite expensive, as it does a linear scan > of 4 KB of memory to find a fat flow. > Once found, it drops the oldest packet of this flow. > > Instead of dropping a single packet, try to drop 50% of the backlog > of this fat flow, with a configurable limit of 64 packets per round. > > TCA_FQ_CODEL_DROP_BATCH_SIZE is the new attribute to make this > limit configurable. > > With this strategy the 4 KB search is amortized to a single cache line > per drop [1], so fq_codel_drop() no longer appears at the top of kernel > profile in presence of few inelastic flows. > > [1] Assuming a 64byte cache line, and 1024 buckets > > Signed-off-by: Eric Dumazet <eduma...@google.com> > Reported-by: Dave Taht <dave.t...@gmail.com> > Cc: Jonathan Morton <chromati...@gmail.com> Applied, thanks Eric.
