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codel: generalize the implementation
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This strips out qdisc specific bits from the code
and makes it slightly more reusable. Codel will be
used by wireless/mac80211 in the future.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Michal Kazior authored and David S. Miller committed Apr 25, 2016
1 parent e425974 commit 79bdc4c
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Showing 3 changed files with 71 additions and 32 deletions.
64 changes: 39 additions & 25 deletions include/net/codel.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -176,12 +176,10 @@ struct codel_stats {

#define CODEL_DISABLED_THRESHOLD INT_MAX

static void codel_params_init(struct codel_params *params,
const struct Qdisc *sch)
static void codel_params_init(struct codel_params *params)
{
params->interval = MS2TIME(100);
params->target = MS2TIME(5);
params->mtu = psched_mtu(qdisc_dev(sch));
params->ce_threshold = CODEL_DISABLED_THRESHOLD;
params->ecn = false;
}
Expand Down Expand Up @@ -226,28 +224,38 @@ static codel_time_t codel_control_law(codel_time_t t,
return t + reciprocal_scale(interval, rec_inv_sqrt << REC_INV_SQRT_SHIFT);
}

typedef u32 (*codel_skb_len_t)(const struct sk_buff *skb);
typedef codel_time_t (*codel_skb_time_t)(const struct sk_buff *skb);
typedef void (*codel_skb_drop_t)(struct sk_buff *skb, void *ctx);
typedef struct sk_buff * (*codel_skb_dequeue_t)(struct codel_vars *vars,
void *ctx);

static bool codel_should_drop(const struct sk_buff *skb,
struct Qdisc *sch,
void *ctx,
struct codel_vars *vars,
struct codel_params *params,
struct codel_stats *stats,
codel_skb_len_t skb_len_func,
codel_skb_time_t skb_time_func,
u32 *backlog,
codel_time_t now)
{
bool ok_to_drop;
u32 skb_len;

if (!skb) {
vars->first_above_time = 0;
return false;
}

vars->ldelay = now - codel_get_enqueue_time(skb);
sch->qstats.backlog -= qdisc_pkt_len(skb);
skb_len = skb_len_func(skb);
vars->ldelay = now - skb_time_func(skb);

if (unlikely(qdisc_pkt_len(skb) > stats->maxpacket))
stats->maxpacket = qdisc_pkt_len(skb);
if (unlikely(skb_len > stats->maxpacket))
stats->maxpacket = skb_len;

if (codel_time_before(vars->ldelay, params->target) ||
sch->qstats.backlog <= params->mtu) {
*backlog <= params->mtu) {
/* went below - stay below for at least interval */
vars->first_above_time = 0;
return false;
Expand All @@ -264,16 +272,17 @@ static bool codel_should_drop(const struct sk_buff *skb,
return ok_to_drop;
}

typedef struct sk_buff * (*codel_skb_dequeue_t)(struct codel_vars *vars,
struct Qdisc *sch);

static struct sk_buff *codel_dequeue(struct Qdisc *sch,
static struct sk_buff *codel_dequeue(void *ctx,
u32 *backlog,
struct codel_params *params,
struct codel_vars *vars,
struct codel_stats *stats,
codel_skb_len_t skb_len_func,
codel_skb_time_t skb_time_func,
codel_skb_drop_t drop_func,
codel_skb_dequeue_t dequeue_func)
{
struct sk_buff *skb = dequeue_func(vars, sch);
struct sk_buff *skb = dequeue_func(vars, ctx);
codel_time_t now;
bool drop;

Expand All @@ -282,7 +291,8 @@ static struct sk_buff *codel_dequeue(struct Qdisc *sch,
return skb;
}
now = codel_get_time();
drop = codel_should_drop(skb, sch, vars, params, stats, now);
drop = codel_should_drop(skb, ctx, vars, params, stats,
skb_len_func, skb_time_func, backlog, now);
if (vars->dropping) {
if (!drop) {
/* sojourn time below target - leave dropping state */
Expand Down Expand Up @@ -310,12 +320,15 @@ static struct sk_buff *codel_dequeue(struct Qdisc *sch,
vars->rec_inv_sqrt);
goto end;
}
stats->drop_len += qdisc_pkt_len(skb);
qdisc_drop(skb, sch);
stats->drop_len += skb_len_func(skb);
drop_func(skb, ctx);
stats->drop_count++;
skb = dequeue_func(vars, sch);
if (!codel_should_drop(skb, sch,
vars, params, stats, now)) {
skb = dequeue_func(vars, ctx);
if (!codel_should_drop(skb, ctx,
vars, params, stats,
skb_len_func,
skb_time_func,
backlog, now)) {
/* leave dropping state */
vars->dropping = false;
} else {
Expand All @@ -333,13 +346,14 @@ static struct sk_buff *codel_dequeue(struct Qdisc *sch,
if (params->ecn && INET_ECN_set_ce(skb)) {
stats->ecn_mark++;
} else {
stats->drop_len += qdisc_pkt_len(skb);
qdisc_drop(skb, sch);
stats->drop_len += skb_len_func(skb);
drop_func(skb, ctx);
stats->drop_count++;

skb = dequeue_func(vars, sch);
drop = codel_should_drop(skb, sch, vars, params,
stats, now);
skb = dequeue_func(vars, ctx);
drop = codel_should_drop(skb, ctx, vars, params,
stats, skb_len_func,
skb_time_func, backlog, now);
}
vars->dropping = true;
/* if min went above target close to when we last went below it
Expand Down
20 changes: 17 additions & 3 deletions net/sched/sch_codel.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -64,20 +64,33 @@ struct codel_sched_data {
* to dequeue a packet from queue. Note: backlog is handled in
* codel, we dont need to reduce it here.
*/
static struct sk_buff *dequeue(struct codel_vars *vars, struct Qdisc *sch)
static struct sk_buff *dequeue_func(struct codel_vars *vars, void *ctx)
{
struct Qdisc *sch = ctx;
struct sk_buff *skb = __skb_dequeue(&sch->q);

if (skb)
sch->qstats.backlog -= qdisc_pkt_len(skb);

prefetch(&skb->end); /* we'll need skb_shinfo() */
return skb;
}

static void drop_func(struct sk_buff *skb, void *ctx)
{
struct Qdisc *sch = ctx;

qdisc_drop(skb, sch);
}

static struct sk_buff *codel_qdisc_dequeue(struct Qdisc *sch)
{
struct codel_sched_data *q = qdisc_priv(sch);
struct sk_buff *skb;

skb = codel_dequeue(sch, &q->params, &q->vars, &q->stats, dequeue);
skb = codel_dequeue(sch, &sch->qstats.backlog, &q->params, &q->vars,
&q->stats, qdisc_pkt_len, codel_get_enqueue_time,
drop_func, dequeue_func);

/* We cant call qdisc_tree_reduce_backlog() if our qlen is 0,
* or HTB crashes. Defer it for next round.
Expand Down Expand Up @@ -173,9 +186,10 @@ static int codel_init(struct Qdisc *sch, struct nlattr *opt)

sch->limit = DEFAULT_CODEL_LIMIT;

codel_params_init(&q->params, sch);
codel_params_init(&q->params);
codel_vars_init(&q->vars);
codel_stats_init(&q->stats);
q->params.mtu = psched_mtu(qdisc_dev(sch));

if (opt) {
int err = codel_change(sch, opt);
Expand Down
19 changes: 15 additions & 4 deletions net/sched/sch_fq_codel.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -220,8 +220,9 @@ static int fq_codel_enqueue(struct sk_buff *skb, struct Qdisc *sch)
* to dequeue a packet from queue. Note: backlog is handled in
* codel, we dont need to reduce it here.
*/
static struct sk_buff *dequeue(struct codel_vars *vars, struct Qdisc *sch)
static struct sk_buff *dequeue_func(struct codel_vars *vars, void *ctx)
{
struct Qdisc *sch = ctx;
struct fq_codel_sched_data *q = qdisc_priv(sch);
struct fq_codel_flow *flow;
struct sk_buff *skb = NULL;
Expand All @@ -231,10 +232,18 @@ static struct sk_buff *dequeue(struct codel_vars *vars, struct Qdisc *sch)
skb = dequeue_head(flow);
q->backlogs[flow - q->flows] -= qdisc_pkt_len(skb);
sch->q.qlen--;
sch->qstats.backlog -= qdisc_pkt_len(skb);
}
return skb;
}

static void drop_func(struct sk_buff *skb, void *ctx)
{
struct Qdisc *sch = ctx;

qdisc_drop(skb, sch);
}

static struct sk_buff *fq_codel_dequeue(struct Qdisc *sch)
{
struct fq_codel_sched_data *q = qdisc_priv(sch);
Expand Down Expand Up @@ -263,8 +272,9 @@ static struct sk_buff *fq_codel_dequeue(struct Qdisc *sch)
prev_ecn_mark = q->cstats.ecn_mark;
prev_backlog = sch->qstats.backlog;

skb = codel_dequeue(sch, &q->cparams, &flow->cvars, &q->cstats,
dequeue);
skb = codel_dequeue(sch, &sch->qstats.backlog, &q->cparams,
&flow->cvars, &q->cstats, qdisc_pkt_len,
codel_get_enqueue_time, drop_func, dequeue_func);

flow->dropped += q->cstats.drop_count - prev_drop_count;
flow->dropped += q->cstats.ecn_mark - prev_ecn_mark;
Expand Down Expand Up @@ -423,9 +433,10 @@ static int fq_codel_init(struct Qdisc *sch, struct nlattr *opt)
q->perturbation = prandom_u32();
INIT_LIST_HEAD(&q->new_flows);
INIT_LIST_HEAD(&q->old_flows);
codel_params_init(&q->cparams, sch);
codel_params_init(&q->cparams);
codel_stats_init(&q->cstats);
q->cparams.ecn = true;
q->cparams.mtu = psched_mtu(qdisc_dev(sch));

if (opt) {
int err = fq_codel_change(sch, opt);
Expand Down

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