Leaving powersave enabled while the scan is suspended requires the use
of PS-Poll to retrieve frames buffered at the AP. PS-Poll isn't a very
efficient means of data transfer and may not even work with drivers not
supporting powersave. These problems can largely be avoided by simply
disabling off-channel powersave when the scan is suspended and enabling
it again when returning to off-channel operation.
The results of this change are fantastic. Previously when using iperf I
would see greatly decreased throughput (often dropping to 0 bits/sec for
several seconds) and very high packet loss during software scans. This
patch completely eliminates the packet loss and reduces the loss in
throughput to very reasonable levels.
Signed-off-by: Seth Forshee <seth.forshee@xxxxxxxxxxxxx>
---
net/mac80211/scan.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
index a875f74..f982dda 100644
--- a/net/mac80211/scan.c
+++ b/net/mac80211/scan.c
@@ -699,11 +699,11 @@ static void ieee80211_scan_state_suspend(struct ieee80211_local *local,
ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL);
/*
- * Re-enable vifs and beaconing. Leave PS
- * in off-channel state..will put that back
- * on-channel at the end of scanning.
+ * Re-enable vifs and beaconing. Disable PS
+ * while the scan is suspended for more
+ * efficient frame rx than with PS-Poll.
*/
- ieee80211_offchannel_return(local, false);
+ ieee80211_offchannel_return(local, true);
*next_delay = HZ / 5;
/* afterwards, resume scan & go to next channel */
@@ -713,8 +713,8 @@ static void ieee80211_scan_state_suspend(struct ieee80211_local *local,
static void ieee80211_scan_state_resume(struct ieee80211_local *local,
unsigned long *next_delay)
{
- /* PS already is in off-channel mode */
- ieee80211_offchannel_stop_vifs(local, false);
+ /* Put PS back in off-channel mode */
+ ieee80211_offchannel_stop_vifs(local, true);
if (local->ops->flush) {
drv_flush(local, false);
--
1.7.9.5
--
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