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codel: split into multiple files
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It was impossible to include codel.h for the
purpose of having access to codel_params or
codel_vars structure definitions and using them
for embedding in other more complex structures.

This splits allows codel.h itself to be treated
like any other header file while codel_qdisc.h and
codel_impl.h contain function definitions with
logic that was previously in codel.h.

This copies over copyrights and doesn't involve
code changes other than adding a few additional
include directives to net/sched/sch*codel.c.

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 79bdc4c commit d068ca2
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Showing 5 changed files with 332 additions and 223 deletions.
223 changes: 0 additions & 223 deletions include/net/codel.h
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Original file line number Diff line number Diff line change
Expand Up @@ -87,27 +87,6 @@ static inline codel_time_t codel_get_time(void)
((s32)((a) - (b)) >= 0))
#define codel_time_before_eq(a, b) codel_time_after_eq(b, a)

/* Qdiscs using codel plugin must use codel_skb_cb in their own cb[] */
struct codel_skb_cb {
codel_time_t enqueue_time;
};

static struct codel_skb_cb *get_codel_cb(const struct sk_buff *skb)
{
qdisc_cb_private_validate(skb, sizeof(struct codel_skb_cb));
return (struct codel_skb_cb *)qdisc_skb_cb(skb)->data;
}

static codel_time_t codel_get_enqueue_time(const struct sk_buff *skb)
{
return get_codel_cb(skb)->enqueue_time;
}

static void codel_set_enqueue_time(struct sk_buff *skb)
{
get_codel_cb(skb)->enqueue_time = codel_get_time();
}

static inline u32 codel_time_to_us(codel_time_t val)
{
u64 valns = ((u64)val << CODEL_SHIFT);
Expand Down Expand Up @@ -176,212 +155,10 @@ struct codel_stats {

#define CODEL_DISABLED_THRESHOLD INT_MAX

static void codel_params_init(struct codel_params *params)
{
params->interval = MS2TIME(100);
params->target = MS2TIME(5);
params->ce_threshold = CODEL_DISABLED_THRESHOLD;
params->ecn = false;
}

static void codel_vars_init(struct codel_vars *vars)
{
memset(vars, 0, sizeof(*vars));
}

static void codel_stats_init(struct codel_stats *stats)
{
stats->maxpacket = 0;
}

/*
* http://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Iterative_methods_for_reciprocal_square_roots
* new_invsqrt = (invsqrt / 2) * (3 - count * invsqrt^2)
*
* Here, invsqrt is a fixed point number (< 1.0), 32bit mantissa, aka Q0.32
*/
static void codel_Newton_step(struct codel_vars *vars)
{
u32 invsqrt = ((u32)vars->rec_inv_sqrt) << REC_INV_SQRT_SHIFT;
u32 invsqrt2 = ((u64)invsqrt * invsqrt) >> 32;
u64 val = (3LL << 32) - ((u64)vars->count * invsqrt2);

val >>= 2; /* avoid overflow in following multiply */
val = (val * invsqrt) >> (32 - 2 + 1);

vars->rec_inv_sqrt = val >> REC_INV_SQRT_SHIFT;
}

/*
* CoDel control_law is t + interval/sqrt(count)
* We maintain in rec_inv_sqrt the reciprocal value of sqrt(count) to avoid
* both sqrt() and divide operation.
*/
static codel_time_t codel_control_law(codel_time_t t,
codel_time_t interval,
u32 rec_inv_sqrt)
{
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,
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;
}

skb_len = skb_len_func(skb);
vars->ldelay = now - skb_time_func(skb);

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

if (codel_time_before(vars->ldelay, params->target) ||
*backlog <= params->mtu) {
/* went below - stay below for at least interval */
vars->first_above_time = 0;
return false;
}
ok_to_drop = false;
if (vars->first_above_time == 0) {
/* just went above from below. If we stay above
* for at least interval we'll say it's ok to drop
*/
vars->first_above_time = now + params->interval;
} else if (codel_time_after(now, vars->first_above_time)) {
ok_to_drop = true;
}
return ok_to_drop;
}

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, ctx);
codel_time_t now;
bool drop;

if (!skb) {
vars->dropping = false;
return skb;
}
now = codel_get_time();
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 */
vars->dropping = false;
} else if (codel_time_after_eq(now, vars->drop_next)) {
/* It's time for the next drop. Drop the current
* packet and dequeue the next. The dequeue might
* take us out of dropping state.
* If not, schedule the next drop.
* A large backlog might result in drop rates so high
* that the next drop should happen now,
* hence the while loop.
*/
while (vars->dropping &&
codel_time_after_eq(now, vars->drop_next)) {
vars->count++; /* dont care of possible wrap
* since there is no more divide
*/
codel_Newton_step(vars);
if (params->ecn && INET_ECN_set_ce(skb)) {
stats->ecn_mark++;
vars->drop_next =
codel_control_law(vars->drop_next,
params->interval,
vars->rec_inv_sqrt);
goto end;
}
stats->drop_len += skb_len_func(skb);
drop_func(skb, ctx);
stats->drop_count++;
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 {
/* and schedule the next drop */
vars->drop_next =
codel_control_law(vars->drop_next,
params->interval,
vars->rec_inv_sqrt);
}
}
}
} else if (drop) {
u32 delta;

if (params->ecn && INET_ECN_set_ce(skb)) {
stats->ecn_mark++;
} else {
stats->drop_len += skb_len_func(skb);
drop_func(skb, ctx);
stats->drop_count++;

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
* assume that the drop rate that controlled the queue on the
* last cycle is a good starting point to control it now.
*/
delta = vars->count - vars->lastcount;
if (delta > 1 &&
codel_time_before(now - vars->drop_next,
16 * params->interval)) {
vars->count = delta;
/* we dont care if rec_inv_sqrt approximation
* is not very precise :
* Next Newton steps will correct it quadratically.
*/
codel_Newton_step(vars);
} else {
vars->count = 1;
vars->rec_inv_sqrt = ~0U >> REC_INV_SQRT_SHIFT;
}
vars->lastcount = vars->count;
vars->drop_next = codel_control_law(now, params->interval,
vars->rec_inv_sqrt);
}
end:
if (skb && codel_time_after(vars->ldelay, params->ce_threshold) &&
INET_ECN_set_ce(skb))
stats->ce_mark++;
return skb;
}
#endif
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