queue-4.19/mac80211-change-default-tx_sk_pacing_shift-to-7.patch

   1 From 5c14a4d05f68415af9e41a4e667d1748d41d1baf Mon Sep 17 00:00:00 2001
   2 From: =?UTF-8?q?Toke=20H=C3=B8iland-J=C3=B8rgensen?= <toke@redhat.com>
   3 Date: Thu, 21 Feb 2019 18:29:36 +0100
   4 Subject: mac80211: Change default tx_sk_pacing_shift to 7
   5 MIME-Version: 1.0
   6 Content-Type: text/plain; charset=UTF-8
   7 Content-Transfer-Encoding: 8bit
   8
   9 From: Toke Høiland-Jørgensen <toke@redhat.com>
  10
  11 commit 5c14a4d05f68415af9e41a4e667d1748d41d1baf upstream.
  12
  13 When we did the original tests for the optimal value of sk_pacing_shift, we
  14 came up with 6 ms of buffering as the default. Sadly, 6 is not a power of
  15 two, so when picking the shift value I erred on the size of less buffering
  16 and picked 4 ms instead of 8. This was probably wrong; those 2 ms of extra
  17 buffering makes a larger difference than I thought.
  18
  19 So, change the default pacing shift to 7, which corresponds to 8 ms of
  20 buffering. The point of diminishing returns really kicks in after 8 ms, and
  21 so having this as a default should cut down on the need for extensive
  22 per-device testing and overrides needed in the drivers.
  23
  24 Cc: stable@vger.kernel.org
  25 Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
  26 Signed-off-by: Johannes Berg <johannes.berg@intel.com>
  27 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  28
  29
  30 ---
  31  net/mac80211/tx.c |    4 ++--
  32  1 file changed, 2 insertions(+), 2 deletions(-)
  33
  34 --- a/net/mac80211/tx.c
  35 +++ b/net/mac80211/tx.c
  36 @@ -3614,10 +3614,10 @@ void __ieee80211_subif_start_xmit(struct
  37                 /* We need a bit of data queued to build aggregates properly, so
  38                  * instruct the TCP stack to allow more than a single ms of data
  39                  * to be queued in the stack. The value is a bit-shift of 1
  40 -                * second, so 8 is ~4ms of queued data. Only affects local TCP
  41 +                * second, so 7 is ~8ms of queued data. Only affects local TCP
  42                  * sockets.
  43                  */
  44 -               sk_pacing_shift_update(skb->sk, 8);
  45 +               sk_pacing_shift_update(skb->sk, 7);
  46
  47                 fast_tx = rcu_dereference(sta->fast_tx);
  48