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authorEric Dumazet <edumazet@google.com>2016-09-19 23:39:11 -0400
committerDavid S. Miller <davem@davemloft.net>2016-09-21 00:23:00 -0400
commit77879147a3481babffd7e368d977ab682545a6bd (patch)
tree394b9e60b29282a5e68fcdb852db6d508bc569af /include/uapi
parent6403389211e1f4d40ed963fe47a96fce1a3ba7a9 (diff)
net_sched: sch_fq: add low_rate_threshold parameter
This commit adds to the fq module a low_rate_threshold parameter to insert a delay after all packets if the socket requests a pacing rate below the threshold. This helps achieve more precise control of the sending rate with low-rate paths, especially policers. The basic issue is that if a congestion control module detects a policer at a certain rate, it may want fq to be able to shape to that policed rate. That way the sender can avoid policer drops by having the packets arrive at the policer at or just under the policed rate. The default threshold of 550Kbps was chosen analytically so that for policers or links at 500Kbps or 512Kbps fq would very likely invoke this mechanism, even if the pacing rate was briefly slightly above the available bandwidth. This value was then empirically validated with two years of production testing on YouTube video servers. Signed-off-by: Van Jacobson <vanj@google.com> Signed-off-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Nandita Dukkipati <nanditad@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/uapi')
-rw-r--r--include/uapi/linux/pkt_sched.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/include/uapi/linux/pkt_sched.h b/include/uapi/linux/pkt_sched.h
index 2382eed50278..f8e39dbaa781 100644
--- a/include/uapi/linux/pkt_sched.h
+++ b/include/uapi/linux/pkt_sched.h
@@ -792,6 +792,8 @@ enum {
TCA_FQ_ORPHAN_MASK, /* mask applied to orphaned skb hashes */
+ TCA_FQ_LOW_RATE_THRESHOLD, /* per packet delay under this rate */
+
__TCA_FQ_MAX
};