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| author | Leslie Monis <lesliemonis@gmail.com> | 2020-03-05 00:26:01 +0530 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2020-03-04 13:25:55 -0800 |
| commit | 105e808c1da2a2827a4a374ae6e3003249729eec (patch) | |
| tree | e6045369559f0fb426929d5fee0e22303a7d95e7 /include/net/pie.h | |
| parent | 220d4ac74ed691033b6fe2bd98dc07d6bdece046 (diff) | |
| download | lwn-105e808c1da2a2827a4a374ae6e3003249729eec.tar.gz lwn-105e808c1da2a2827a4a374ae6e3003249729eec.zip | |
pie: remove pie_vars->accu_prob_overflows
The variable pie_vars->accu_prob is used as an accumulator for
probability values. Since probabilty values are scaled using the
MAX_PROB macro denoting (2^64 - 1), pie_vars->accu_prob is
likely to overflow as it is of type u64.
The variable pie_vars->accu_prob_overflows counts the number of
times the variable pie_vars->accu_prob overflows.
The MAX_PROB macro needs to be equal to at least (2^39 - 1) in
order to do precise calculations without any underflow. Thus
MAX_PROB can be reduced to (2^56 - 1) without affecting the
precision in calculations drastically. Doing so will eliminate
the need for the variable pie_vars->accu_prob_overflows as the
variable pie_vars->accu_prob will never overflow.
Removing the variable pie_vars->accu_prob_overflows also reduces
the size of the structure pie_vars to exactly 64 bytes.
Signed-off-by: Mohit P. Tahiliani <tahiliani@nitk.edu.in>
Signed-off-by: Gautam Ramakrishnan <gautamramk@gmail.com>
Signed-off-by: Leslie Monis <lesliemonis@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/net/pie.h')
| -rw-r--r-- | include/net/pie.h | 5 |
1 files changed, 1 insertions, 4 deletions
diff --git a/include/net/pie.h b/include/net/pie.h index 24f68c1e9919..1c645b76a2ed 100644 --- a/include/net/pie.h +++ b/include/net/pie.h @@ -8,7 +8,7 @@ #include <net/inet_ecn.h> #include <net/pkt_sched.h> -#define MAX_PROB U64_MAX +#define MAX_PROB (U64_MAX >> BITS_PER_BYTE) #define DTIME_INVALID U64_MAX #define QUEUE_THRESHOLD 16384 #define DQCOUNT_INVALID -1 @@ -47,7 +47,6 @@ struct pie_params { * @dq_count: number of bytes dequeued in a measurement cycle * @avg_dq_rate: calculated average dq rate * @backlog_old: queue backlog during previous qdelay calculation - * @accu_prob_overflows: number of times accu_prob overflows */ struct pie_vars { psched_time_t qdelay; @@ -59,7 +58,6 @@ struct pie_vars { u64 dq_count; u32 avg_dq_rate; u32 backlog_old; - u8 accu_prob_overflows; }; /** @@ -107,7 +105,6 @@ static inline void pie_vars_init(struct pie_vars *vars) vars->accu_prob = 0; vars->dq_count = DQCOUNT_INVALID; vars->avg_dq_rate = 0; - vars->accu_prob_overflows = 0; } static inline struct pie_skb_cb *get_pie_cb(const struct sk_buff *skb) |