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authorMohit P. Tahiliani <tahiliani@nitk.edu.in>2019-02-26 00:39:59 +0530
committerDavid S. Miller <davem@davemloft.net>2019-02-25 14:21:03 -0800
commit3f7ae5f3dc5295ac17d6521130ed8a8f8a723fbf (patch)
tree3529f45b5398596453548eac690b8808caa4090e /net/sched/sch_pie.c
parentnet: sched: pie: change initial value of pie_vars->burst_time (diff)
downloadlinux-dev-3f7ae5f3dc5295ac17d6521130ed8a8f8a723fbf.tar.xz
linux-dev-3f7ae5f3dc5295ac17d6521130ed8a8f8a723fbf.zip
net: sched: pie: add more cases to auto-tune alpha and beta
The current implementation scales the local alpha and beta variables in the calculate_probability function by the same amount for all values of drop probability below 1%. RFC 8033 suggests using additional cases for auto-tuning alpha and beta when the drop probability is less than 1%. In order to add more auto-tuning cases, MAX_PROB must be scaled by u64 instead of u32 to prevent underflow when scaling the local alpha and beta variables in the calculate_probability function. Signed-off-by: Mohit P. Tahiliani <tahiliani@nitk.edu.in> Signed-off-by: Dhaval Khandla <dhavaljkhandla26@gmail.com> Signed-off-by: Hrishikesh Hiraskar <hrishihiraskar@gmail.com> Signed-off-by: Manish Kumar B <bmanish15597@gmail.com> Signed-off-by: Sachin D. Patil <sdp.sachin@gmail.com> Signed-off-by: Leslie Monis <lesliemonis@gmail.com> Acked-by: Dave Taht <dave.taht@gmail.com> Acked-by: Jamal Hadi Salim <jhs@mojatatu.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to '')
-rw-r--r--net/sched/sch_pie.c65
1 files changed, 32 insertions, 33 deletions
diff --git a/net/sched/sch_pie.c b/net/sched/sch_pie.c
index d88ab53593b3..30f158582499 100644
--- a/net/sched/sch_pie.c
+++ b/net/sched/sch_pie.c
@@ -33,7 +33,7 @@
#define QUEUE_THRESHOLD 16384
#define DQCOUNT_INVALID -1
-#define MAX_PROB 0xffffffff
+#define MAX_PROB 0xffffffffffffffff
#define PIE_SCALE 8
/* parameters used */
@@ -49,7 +49,7 @@ struct pie_params {
/* variables used */
struct pie_vars {
- u32 prob; /* probability but scaled by u32 limit. */
+ u64 prob; /* probability but scaled by u64 limit. */
psched_time_t burst_time;
psched_time_t qdelay;
psched_time_t qdelay_old;
@@ -99,8 +99,8 @@ static void pie_vars_init(struct pie_vars *vars)
static bool drop_early(struct Qdisc *sch, u32 packet_size)
{
struct pie_sched_data *q = qdisc_priv(sch);
- u32 rnd;
- u32 local_prob = q->vars.prob;
+ u64 rnd;
+ u64 local_prob = q->vars.prob;
u32 mtu = psched_mtu(qdisc_dev(sch));
/* If there is still burst allowance left skip random early drop */
@@ -124,11 +124,11 @@ static bool drop_early(struct Qdisc *sch, u32 packet_size)
* probablity. Smaller packets will have lower drop prob in this case
*/
if (q->params.bytemode && packet_size <= mtu)
- local_prob = (local_prob / mtu) * packet_size;
+ local_prob = (u64)packet_size * div_u64(local_prob, mtu);
else
local_prob = q->vars.prob;
- rnd = prandom_u32();
+ prandom_bytes(&rnd, 8);
if (rnd < local_prob)
return true;
@@ -317,9 +317,10 @@ static void calculate_probability(struct Qdisc *sch)
u32 qlen = sch->qstats.backlog; /* queue size in bytes */
psched_time_t qdelay = 0; /* in pschedtime */
psched_time_t qdelay_old = q->vars.qdelay; /* in pschedtime */
- s32 delta = 0; /* determines the change in probability */
- u32 oldprob;
- u32 alpha, beta;
+ s64 delta = 0; /* determines the change in probability */
+ u64 oldprob;
+ u64 alpha, beta;
+ u32 power;
bool update_prob = true;
q->vars.qdelay_old = q->vars.qdelay;
@@ -339,38 +340,36 @@ static void calculate_probability(struct Qdisc *sch)
* value for alpha as 0.125. In this implementation, we use values 0-32
* passed from user space to represent this. Also, alpha and beta have
* unit of HZ and need to be scaled before they can used to update
- * probability. alpha/beta are updated locally below by 1) scaling them
- * appropriately 2) scaling down by 16 to come to 0-2 range.
- * Please see paper for details.
- *
- * We scale alpha and beta differently depending on whether we are in
- * light, medium or high dropping mode.
+ * probability. alpha/beta are updated locally below by scaling down
+ * by 16 to come to 0-2 range.
*/
- if (q->vars.prob < MAX_PROB / 100) {
- alpha =
- (q->params.alpha * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 7;
- beta =
- (q->params.beta * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 7;
- } else if (q->vars.prob < MAX_PROB / 10) {
- alpha =
- (q->params.alpha * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 5;
- beta =
- (q->params.beta * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 5;
- } else {
- alpha =
- (q->params.alpha * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 4;
- beta =
- (q->params.beta * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 4;
+ alpha = ((u64)q->params.alpha * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 4;
+ beta = ((u64)q->params.beta * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 4;
+
+ /* We scale alpha and beta differently depending on how heavy the
+ * congestion is. Please see RFC 8033 for details.
+ */
+ if (q->vars.prob < MAX_PROB / 10) {
+ alpha >>= 1;
+ beta >>= 1;
+
+ power = 100;
+ while (q->vars.prob < div_u64(MAX_PROB, power) &&
+ power <= 1000000) {
+ alpha >>= 2;
+ beta >>= 2;
+ power *= 10;
+ }
}
/* alpha and beta should be between 0 and 32, in multiples of 1/16 */
- delta += alpha * ((qdelay - q->params.target));
- delta += beta * ((qdelay - qdelay_old));
+ delta += alpha * (u64)(qdelay - q->params.target);
+ delta += beta * (u64)(qdelay - qdelay_old);
oldprob = q->vars.prob;
/* to ensure we increase probability in steps of no more than 2% */
- if (delta > (s32)(MAX_PROB / (100 / 2)) &&
+ if (delta > (s64)(MAX_PROB / (100 / 2)) &&
q->vars.prob >= MAX_PROB / 10)
delta = (MAX_PROB / 100) * 2;