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| author |   Daniel Halperin <dhalperi@cs.washington.edu> | 2011-05-10 19:00:45 -0700 |
|---|---|---|
| committer |   John W. Linville <linville@tuxdriver.com> | 2011-05-12 14:10:48 -0400 |
| commit | 8fddddff0ad4ccc2787464207eba9ed3063e69cd (patch) | |
| tree | 6f219c46e9fdae5df766deb784c3cfc00e3e4106 /net/mac80211/rc80211_minstrel_ht.c | |
| parent | cfg80211: restrict AP beacon intervals (diff) | |
| download | linux-dev-8fddddff0ad4ccc2787464207eba9ed3063e69cd.tar.xz linux-dev-8fddddff0ad4ccc2787464207eba9ed3063e69cd.zip | |
mac80211: fix contention time computation in minstrel, minstrel_ht
When transmitting a frame, the transmitter waits a random number of
slots between 0 and cw. Thus, the contention time is (cw / 2) * t_slot
which we can represent instead as (cw * t_slot) >> 1. Also fix a few
other accounting bugs around contention time, and add comments.
Signed-off-by: Daniel Halperin <dhalperi@cs.washington.edu>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Diffstat (limited to 'net/mac80211/rc80211_minstrel_ht.c')
| -rw-r--r-- | net/mac80211/rc80211_minstrel_ht.c | 27 |
1 files changed, 21 insertions, 6 deletions
diff --git a/net/mac80211/rc80211_minstrel_ht.c b/net/mac80211/rc80211_minstrel_ht.c index dbdebeda097f..3d09c58938e2 100644 --- a/net/mac80211/rc80211_minstrel_ht.c +++ b/net/mac80211/rc80211_minstrel_ht.c @@ -464,6 +464,7 @@ minstrel_calc_retransmit(struct minstrel_priv *mp, struct minstrel_ht_sta *mi, const struct mcs_group *group; unsigned int tx_time, tx_time_rtscts, tx_time_data; unsigned int cw = mp->cw_min; + unsigned int ctime = 0; unsigned int t_slot = 9; /* FIXME */ unsigned int ampdu_len = MINSTREL_TRUNC(mi->avg_ampdu_len); @@ -480,13 +481,27 @@ minstrel_calc_retransmit(struct minstrel_priv *mp, struct minstrel_ht_sta *mi, group = &minstrel_mcs_groups[index / MCS_GROUP_RATES]; tx_time_data = group->duration[index % MCS_GROUP_RATES] * ampdu_len; - tx_time = 2 * (t_slot + mi->overhead + tx_time_data); - tx_time_rtscts = 2 * (t_slot + mi->overhead_rtscts + tx_time_data); + + /* Contention time for first 2 tries */ + ctime = (t_slot * cw) >> 1; + cw = min((cw << 1) | 1, mp->cw_max); + ctime += (t_slot * cw) >> 1; + cw = min((cw << 1) | 1, mp->cw_max); + + /* Total TX time for data and Contention after first 2 tries */ + tx_time = ctime + 2 * (mi->overhead + tx_time_data); + tx_time_rtscts = ctime + 2 * (mi->overhead_rtscts + tx_time_data); + + /* See how many more tries we can fit inside segment size */ do { - cw = (cw << 1) | 1; - cw = min(cw, mp->cw_max); - tx_time += cw + t_slot + mi->overhead; - tx_time_rtscts += cw + t_slot + mi->overhead_rtscts; + /* Contention time for this try */ + ctime = (t_slot * cw) >> 1; + cw = min((cw << 1) | 1, mp->cw_max); + + /* Total TX time after this try */ + tx_time += ctime + mi->overhead + tx_time_data; + tx_time_rtscts += ctime + mi->overhead_rtscts + tx_time_data; + if (tx_time_rtscts < mp->segment_size) mr->retry_count_rtscts++; } while ((tx_time < mp->segment_size) && |