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  1. 19 Dec, 2013 3 commits
    • Terry Lam's avatar
      net-qdisc-hhf: Heavy-Hitter Filter (HHF) qdisc · 10239edf
      Terry Lam authored 
      This patch implements the first size-based qdisc that attempts to
differentiate between small flows and heavy-hitters.  The goal is to
catch the heavy-hitters and move them to a separate queue with less
priority so that bulk traffic does not affect the latency of critical
traffic.  Currently "less priority" means less weight (2:1 in
particular) in a Weighted Deficit Round Robin (WDRR) scheduler.

In essence, this patch addresses the "delay-bloat" problem due to
bloated buffers. In some systems, large queues may be necessary for
obtaining CPU efficiency, or due to the presence of unresponsive
traffic like UDP, or just a large number of connections with each
having a small amount of outstanding traffic. In these circumstances,
HHF aims to reduce the HoL blocking for latency sensitive traffic,
while not impacting the queues built up by bulk traffic.  HHF can also
be used in conjunction with other AQM mechanisms such as CoDel.

To capture heavy-hitters, we implement the "multi-stage filter" design
in the following paper:
C. Estan and G. Varghese, "New Directions in Traffic Measurement and
Accounting", in ACM SIGCOMM, 2002.

Some configurable qdisc settings through 'tc':
- hhf_reset_timeout: period to reset counter values in the multi-stage
                     filter (default 40ms)
- hhf_admit_bytes:   threshold to classify heavy-hitters
                     (default 128KB)
- hhf_evict_timeout: threshold to evict idle heavy-hitters
                     (default 1s)
- hhf_non_hh_weight: Weighted Deficit Round Robin (WDRR) weight for
                     non-heavy-hitters (default 2)
- hh_flows_limit:    max number of heavy-hitter flow entries
                     (default 2048)

Note that the ratio between hhf_admit_bytes and hhf_reset_timeout
reflects the bandwidth of heavy-hitters that we attempt to capture
(25Mbps with the above default settings).

The false negative rate (heavy-hitter flows getting away unclassified)
is zero by the design of the multi-stage filter algorithm.
With 100 heavy-hitter flows, using four hashes and 4000 counters yields
a false positive rate (non-heavy-hitters mistakenly classified as
heavy-hitters) of less than 1e-4.
Signed-off-by: default avatarTerry Lam <vtlam@google.com>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      10239edf
    • Matthew Whitehead's avatar
      3c59x: Add software timestamping · 2a2529ef
      Matthew Whitehead authored 
      Added software timestamping ability. Tested with linuxptp and synchronized
clocks to an average of less than 200 microseconds on 10 megabit ethernet.

Tested on both Vortex and Boomerang models.
Signed-off-by: default avatarMatthew Whitehead <tedheadster@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      2a2529ef
    • Francesco Fusco's avatar
      lib: hash: follow-up fixups for arch hash · 23721754
      Francesco Fusco authored 
      This patch adds the include file to pull in __read_mostly on some
architectures e.g. ppc and also fixes up signatures in generic
asm.
Reported-by: default avatarFengguang Wu <fengguang.wu@intel.com>
Signed-off-by: default avatarFrancesco Fusco <ffusco@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      23721754
  3. 18 Dec, 2013 37 commits
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