250 lines
6.8 KiB
C
250 lines
6.8 KiB
C
/*
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* net/sched/gen_estimator.c Simple rate estimator.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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* Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
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*
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* Changes:
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* Jamal Hadi Salim - moved it to net/core and reshulfed
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* names to make it usable in general net subsystem.
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*/
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#include <asm/uaccess.h>
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#include <asm/system.h>
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#include <asm/bitops.h>
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#include <linux/module.h>
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <linux/jiffies.h>
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#include <linux/string.h>
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#include <linux/mm.h>
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#include <linux/socket.h>
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#include <linux/sockios.h>
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#include <linux/in.h>
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#include <linux/errno.h>
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#include <linux/interrupt.h>
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#include <linux/netdevice.h>
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#include <linux/skbuff.h>
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#include <linux/rtnetlink.h>
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#include <linux/init.h>
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#include <net/sock.h>
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#include <net/gen_stats.h>
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/*
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This code is NOT intended to be used for statistics collection,
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its purpose is to provide a base for statistical multiplexing
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for controlled load service.
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If you need only statistics, run a user level daemon which
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periodically reads byte counters.
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Unfortunately, rate estimation is not a very easy task.
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F.e. I did not find a simple way to estimate the current peak rate
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and even failed to formulate the problem 8)8)
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So I preferred not to built an estimator into the scheduler,
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but run this task separately.
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Ideally, it should be kernel thread(s), but for now it runs
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from timers, which puts apparent top bounds on the number of rated
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flows, has minimal overhead on small, but is enough
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to handle controlled load service, sets of aggregates.
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We measure rate over A=(1<<interval) seconds and evaluate EWMA:
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avrate = avrate*(1-W) + rate*W
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where W is chosen as negative power of 2: W = 2^(-ewma_log)
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The resulting time constant is:
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T = A/(-ln(1-W))
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NOTES.
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* The stored value for avbps is scaled by 2^5, so that maximal
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rate is ~1Gbit, avpps is scaled by 2^10.
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* Minimal interval is HZ/4=250msec (it is the greatest common divisor
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for HZ=100 and HZ=1024 8)), maximal interval
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is (HZ*2^EST_MAX_INTERVAL)/4 = 8sec. Shorter intervals
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are too expensive, longer ones can be implemented
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at user level painlessly.
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*/
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#define EST_MAX_INTERVAL 5
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struct gen_estimator
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{
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struct gen_estimator *next;
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struct gnet_stats_basic *bstats;
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struct gnet_stats_rate_est *rate_est;
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spinlock_t *stats_lock;
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unsigned interval;
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int ewma_log;
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u64 last_bytes;
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u32 last_packets;
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u32 avpps;
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u32 avbps;
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};
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struct gen_estimator_head
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{
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struct timer_list timer;
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struct gen_estimator *list;
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};
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static struct gen_estimator_head elist[EST_MAX_INTERVAL+1];
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/* Estimator array lock */
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static DEFINE_RWLOCK(est_lock);
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static void est_timer(unsigned long arg)
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{
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int idx = (int)arg;
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struct gen_estimator *e;
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read_lock(&est_lock);
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for (e = elist[idx].list; e; e = e->next) {
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u64 nbytes;
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u32 npackets;
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u32 rate;
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spin_lock(e->stats_lock);
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nbytes = e->bstats->bytes;
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npackets = e->bstats->packets;
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rate = (nbytes - e->last_bytes)<<(7 - idx);
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e->last_bytes = nbytes;
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e->avbps += ((long)rate - (long)e->avbps) >> e->ewma_log;
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e->rate_est->bps = (e->avbps+0xF)>>5;
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rate = (npackets - e->last_packets)<<(12 - idx);
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e->last_packets = npackets;
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e->avpps += ((long)rate - (long)e->avpps) >> e->ewma_log;
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e->rate_est->pps = (e->avpps+0x1FF)>>10;
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spin_unlock(e->stats_lock);
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}
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mod_timer(&elist[idx].timer, jiffies + ((HZ<<idx)/4));
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read_unlock(&est_lock);
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}
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/**
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* gen_new_estimator - create a new rate estimator
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* @bstats: basic statistics
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* @rate_est: rate estimator statistics
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* @stats_lock: statistics lock
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* @opt: rate estimator configuration TLV
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*
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* Creates a new rate estimator with &bstats as source and &rate_est
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* as destination. A new timer with the interval specified in the
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* configuration TLV is created. Upon each interval, the latest statistics
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* will be read from &bstats and the estimated rate will be stored in
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* &rate_est with the statistics lock grabed during this period.
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*
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* Returns 0 on success or a negative error code.
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*/
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int gen_new_estimator(struct gnet_stats_basic *bstats,
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struct gnet_stats_rate_est *rate_est, spinlock_t *stats_lock, struct rtattr *opt)
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{
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struct gen_estimator *est;
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struct gnet_estimator *parm = RTA_DATA(opt);
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if (RTA_PAYLOAD(opt) < sizeof(*parm))
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return -EINVAL;
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if (parm->interval < -2 || parm->interval > 3)
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return -EINVAL;
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est = kzalloc(sizeof(*est), GFP_KERNEL);
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if (est == NULL)
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return -ENOBUFS;
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est->interval = parm->interval + 2;
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est->bstats = bstats;
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est->rate_est = rate_est;
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est->stats_lock = stats_lock;
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est->ewma_log = parm->ewma_log;
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est->last_bytes = bstats->bytes;
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est->avbps = rate_est->bps<<5;
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est->last_packets = bstats->packets;
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est->avpps = rate_est->pps<<10;
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est->next = elist[est->interval].list;
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if (est->next == NULL) {
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init_timer(&elist[est->interval].timer);
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elist[est->interval].timer.data = est->interval;
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elist[est->interval].timer.expires = jiffies + ((HZ<<est->interval)/4);
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elist[est->interval].timer.function = est_timer;
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add_timer(&elist[est->interval].timer);
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}
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write_lock_bh(&est_lock);
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elist[est->interval].list = est;
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write_unlock_bh(&est_lock);
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return 0;
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}
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/**
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* gen_kill_estimator - remove a rate estimator
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* @bstats: basic statistics
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* @rate_est: rate estimator statistics
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*
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* Removes the rate estimator specified by &bstats and &rate_est
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* and deletes the timer.
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*/
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void gen_kill_estimator(struct gnet_stats_basic *bstats,
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struct gnet_stats_rate_est *rate_est)
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{
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int idx;
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struct gen_estimator *est, **pest;
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for (idx=0; idx <= EST_MAX_INTERVAL; idx++) {
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int killed = 0;
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pest = &elist[idx].list;
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while ((est=*pest) != NULL) {
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if (est->rate_est != rate_est || est->bstats != bstats) {
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pest = &est->next;
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continue;
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}
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write_lock_bh(&est_lock);
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*pest = est->next;
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write_unlock_bh(&est_lock);
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kfree(est);
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killed++;
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}
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if (killed && elist[idx].list == NULL)
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del_timer(&elist[idx].timer);
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}
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}
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/**
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* gen_replace_estimator - replace rate estimator configruation
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* @bstats: basic statistics
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* @rate_est: rate estimator statistics
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* @stats_lock: statistics lock
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* @opt: rate estimator configuration TLV
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*
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* Replaces the configuration of a rate estimator by calling
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* gen_kill_estimator() and gen_new_estimator().
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*
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* Returns 0 on success or a negative error code.
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*/
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int
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gen_replace_estimator(struct gnet_stats_basic *bstats,
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struct gnet_stats_rate_est *rate_est, spinlock_t *stats_lock,
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struct rtattr *opt)
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{
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gen_kill_estimator(bstats, rate_est);
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return gen_new_estimator(bstats, rate_est, stats_lock, opt);
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}
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EXPORT_SYMBOL(gen_kill_estimator);
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EXPORT_SYMBOL(gen_new_estimator);
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EXPORT_SYMBOL(gen_replace_estimator);
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