On 2013-03-04 7:48 PM, Thomas Huehn wrote:
> While minstrel bootstraps and fills the success probabilities of each
> rate the lowest rate has typically a very high success probability
> (often 100% in our tests).
> Its statistics are never updated but considered to setup the mrr chain.
> In our tests we see that especially the 3rd mrr stage (which is that
> rate providing highest success probability) is filled with the lowest rate
> because its initial high sucess probability is never updated. By design
> the 4th mrr stage is filled with the lowest rate so often 3rd and 4th
> mrr stage are equal.
>
> This patch follows minstrels general approach of assuming as little
> as possible about rate dependencies. Consequently we include the
> lowest rate into the random sampling table to get balanced up-to-date
> statistics of all rates and therefore balanced decisions.
>
> Signed-off-by: Thomas Huehn <thomas@xxxxxxxxxxxxxxxxxxxxxxx>
> ---
> net/mac80211/rc80211_minstrel.c | 20 +++++++-------------
> net/mac80211/rc80211_minstrel.h | 4 +++-
> net/mac80211/rc80211_minstrel_ht.c | 1 -
> 3 files changed, 10 insertions(+), 15 deletions(-)
>
> diff --git a/net/mac80211/rc80211_minstrel.c b/net/mac80211/rc80211_minstrel.c
> index aa59f29..aa1e81a 100644
> --- a/net/mac80211/rc80211_minstrel.c
> +++ b/net/mac80211/rc80211_minstrel.c
> @@ -370,26 +369,21 @@ static void
> init_sample_table(struct minstrel_sta_info *mi)
> {
> unsigned int i, col, new_idx;
> - unsigned int n_srates = mi->n_rates - 1;
> u8 rnd[8];
>
> mi->sample_column = 0;
> mi->sample_row = 0;
> - memset(mi->sample_table, 0, SAMPLE_COLUMNS * mi->n_rates);
> + memset(mi->sample_table, 0xff, SAMPLE_COLUMNS * mi->n_rates);
>
> for (col = 0; col < SAMPLE_COLUMNS; col++) {
> - for (i = 0; i < n_srates; i++) {
> + for (i = 0; i < mi->n_rates; i++) {
> get_random_bytes(rnd, sizeof(rnd));
> - new_idx = (i + rnd[i & 7]) % n_srates;
> + new_idx = (i + rnd[i]) % mi->n_rates;
Don't remove the '& 7' part, otherwise the rnd array will overflow.
There's no need for it to be as big as the number of rates though.
Also, there's a typo in the subject line: 'randmon'.
- Felix
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