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/* vim:ts=8:sts=8:sw=4:noai:noexpandtab
*
* Rate regulation.
*
* Copyright (c) 2006-2010 Miru Limited.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include <impl/framework.h>
/* create machinery for rate regulation.
* the rate_per_sec is ammortized over millisecond time periods.
*
* NB: bucket MUST be memset 0 before calling.
*/
void
pgm_rate_create (
pgm_rate_t* bucket,
const ssize_t rate_per_sec, /* 0 = disable */
const size_t iphdr_len,
const uint16_t max_tpdu
)
{
/* pre-conditions */
pgm_assert (NULL != bucket);
pgm_assert (rate_per_sec >= max_tpdu);
bucket->rate_per_sec = rate_per_sec;
bucket->iphdr_len = iphdr_len;
bucket->last_rate_check = pgm_time_update_now ();
/* pre-fill bucket */
if ((rate_per_sec / 1000) >= max_tpdu) {
bucket->rate_per_msec = bucket->rate_per_sec / 1000;
bucket->rate_limit = bucket->rate_per_msec;
} else {
bucket->rate_limit = bucket->rate_per_sec;
}
pgm_spinlock_init (&bucket->spinlock);
}
void
pgm_rate_destroy (
pgm_rate_t* bucket
)
{
/* pre-conditions */
pgm_assert (NULL != bucket);
pgm_spinlock_free (&bucket->spinlock);
}
/* check bit bucket whether an operation can proceed or should wait.
*
* returns TRUE when leaky bucket permits unless non-blocking flag is set.
* returns FALSE if operation should block and non-blocking flag is set.
*/
bool
pgm_rate_check (
pgm_rate_t* bucket,
const size_t data_size,
const bool is_nonblocking
)
{
int64_t new_rate_limit;
/* pre-conditions */
pgm_assert (NULL != bucket);
pgm_assert (data_size > 0);
if (0 == bucket->rate_per_sec)
return TRUE;
pgm_spinlock_lock (&bucket->spinlock);
pgm_time_t now = pgm_time_update_now();
pgm_time_t time_since_last_rate_check = now - bucket->last_rate_check;
if (bucket->rate_per_msec)
{
if (time_since_last_rate_check > pgm_msecs(1))
new_rate_limit = bucket->rate_per_msec;
else {
new_rate_limit = bucket->rate_limit + ((bucket->rate_per_msec * time_since_last_rate_check) / 1000UL);
if (new_rate_limit > bucket->rate_per_msec)
new_rate_limit = bucket->rate_per_msec;
}
}
else
{
if (time_since_last_rate_check > pgm_secs(1))
new_rate_limit = bucket->rate_per_sec;
else {
new_rate_limit = bucket->rate_limit + ((bucket->rate_per_sec * time_since_last_rate_check) / 1000000UL);
if (new_rate_limit > bucket->rate_per_sec)
new_rate_limit = bucket->rate_per_sec;
}
}
new_rate_limit -= ( bucket->iphdr_len + data_size );
if (is_nonblocking && new_rate_limit < 0) {
pgm_spinlock_unlock (&bucket->spinlock);
return FALSE;
}
bucket->rate_limit = new_rate_limit;
bucket->last_rate_check = now;
if (bucket->rate_limit < 0) {
ssize_t sleep_amount;
do {
pgm_thread_yield();
now = pgm_time_update_now();
time_since_last_rate_check = now - bucket->last_rate_check;
sleep_amount = (ssize_t)pgm_to_secs (bucket->rate_per_sec * time_since_last_rate_check);
} while (sleep_amount + bucket->rate_limit < 0);
bucket->rate_limit += sleep_amount;
bucket->last_rate_check = now;
}
pgm_spinlock_unlock (&bucket->spinlock);
return TRUE;
}
pgm_time_t
pgm_rate_remaining (
pgm_rate_t* bucket,
const size_t n
)
{
/* pre-conditions */
pgm_assert (NULL != bucket);
if (PGM_UNLIKELY(0 == bucket->rate_per_sec))
return 0;
pgm_spinlock_lock (&bucket->spinlock);
const pgm_time_t now = pgm_time_update_now();
const pgm_time_t time_since_last_rate_check = now - bucket->last_rate_check;
const int64_t bucket_bytes = bucket->rate_limit + pgm_to_secs (bucket->rate_per_sec * time_since_last_rate_check) - n;
pgm_spinlock_unlock (&bucket->spinlock);
return bucket_bytes >= 0 ? 0 : (bucket->rate_per_sec / -bucket_bytes);
}
/* eof */
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