On Wed, 2013-01-23 at 12:32 +0100, Stanislaw Gruszka wrote: > Patch vastly improve latency while scanning. Slight throughput > improvements were observed as well. Is intended for improve performance > of voice and video applications, when scan is periodically requested by > user space (i.e. default NetworkManager behaviour). > > Patch remove latency requirement based on PM_QOS_NETWORK_LATENCY, > this value is 2000 seconds by default (i.e. approximately 0.5 hour !?!). > > Also remove listen interval requirement, which based on beaconing and > depending on BSS parameters. It can make we stay off-channel for a > second or more. > > Instead try to offer the best latency that we could, i.e. be off-channel > no longer than PASSIVE channel scan time: 125 ms. That mean we will > scan two ACTIVE channels and go back to on-channel, and one PASSIVE > channel, and go back to on-channel. > > Patch also decrease PASSIVE channel scan time to about 110 ms. > > As drawback patch increase overall scan time. On my tests, when scanning > both 2GHz and 5GHz bands, scanning time increase from 5 seconds up to 10 > seconds. Since that increase happen only when we are associated, I think > it can be acceptable. If eventually better scan time is needed for > situations when we lose signal and quickly need to decide to which AP > roam, additional scan flag or parameter can be introduced. > > I tested patch by doing: > > while true; do iw dev wlan0 scan; sleep 3; done > /dev/null > > and > > ping -i0.2 -c 1000 HOST > > on remote and local machine, results are as below: > > * Ping from local periodically scanning machine to AP: > Unpatched: rtt min/avg/max/mdev = 0.928/24.946/182.135/36.873 ms > Patched: rtt min/avg/max/mdev = 0.928/19.678/150.845/33.130 ms > > * Ping from remote machine to periodically scanning machine: > Unpatched: rtt min/avg/max/mdev = 1.637/120.683/709.139/164.337 ms > Patched: rtt min/avg/max/mdev = 1.807/26.893/201.435/40.284 ms > > Throughput measured by scp show following results. > > * Upload to periodically scanning machine: > Unpatched: 3.9MB/s 03:15 > Patched: 4.3MB/s 02:58 > > * Download from periodically scanning machine: > Unpatched: 5.5MB/s 02:17 > Patched: 6.2MB/s 02:02 Applied. johannes -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
