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Subject[PATCH 4.20 161/183] mac80211: Change default tx_sk_pacing_shift to 7
4.20-stable review patch.  If anyone has any objections, please let me know.


From: Toke Høiland-Jørgensen <>

commit 5c14a4d05f68415af9e41a4e667d1748d41d1baf upstream.

When we did the original tests for the optimal value of sk_pacing_shift, we
came up with 6 ms of buffering as the default. Sadly, 6 is not a power of
two, so when picking the shift value I erred on the size of less buffering
and picked 4 ms instead of 8. This was probably wrong; those 2 ms of extra
buffering makes a larger difference than I thought.

So, change the default pacing shift to 7, which corresponds to 8 ms of
buffering. The point of diminishing returns really kicks in after 8 ms, and
so having this as a default should cut down on the need for extensive
per-device testing and overrides needed in the drivers.

Signed-off-by: Toke Høiland-Jørgensen <>
Signed-off-by: Johannes Berg <>
Signed-off-by: Greg Kroah-Hartman <>

net/mac80211/main.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/mac80211/main.c
+++ b/net/mac80211/main.c
@@ -615,13 +615,13 @@ struct ieee80211_hw *ieee80211_alloc_hw_
* We need a bit of data queued to build aggregates properly, so
* instruct the TCP stack to allow more than a single ms of data
* to be queued in the stack. The value is a bit-shift of 1
- * second, so 8 is ~4ms of queued data. Only affects local TCP
+ * second, so 7 is ~8ms of queued data. Only affects local TCP
* sockets.
* This is the default, anyhow - drivers may need to override it
* for local reasons (longer buffers, longer completion time, or
* similar).
- local->hw.tx_sk_pacing_shift = 8;
+ local->hw.tx_sk_pacing_shift = 7;

/* set up some defaults */
local->hw.queues = 1;

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