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Commit 511e11e3 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
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pkt_sched: gen_estimator: use 64 bit intermediate counters for bps 



gen_estimator can overflow bps (bytes per second) with Gb links, while
it was designed with a u32 API, with a theorical limit of 34360Mbit
(2^32 bytes)

Using 64 bit intermediate avbps/brate counters can allow us to reach
this theorical limit.

Signed-off-by: default avatarEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: default avatarJarek Poplawski <jarkao2@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c4ca2374

net/core/gen_estimator.c

+7 −6
Original line number Diff line number Diff line
@@ -66,9 +66,9 @@ 


   NOTES.



   * The stored value for avbps is scaled by 2^5, so that maximal

     rate is ~1Gbit, avpps is scaled by 2^10.



   * avbps is scaled by 2^5, avpps is scaled by 2^10.

   * both values are reported as 32 bit unsigned values. bps can

     overflow for fast links : max speed being 34360Mbit/sec

   * Minimal interval is HZ/4=250msec (it is the greatest common divisor

     for HZ=100 and HZ=1024 8)), maximal interval

     is (HZ*2^EST_MAX_INTERVAL)/4 = 8sec. Shorter intervals
@@ -86,9 +86,9 @@ struct gen_estimator 
	spinlock_t		*stats_lock;

	int			ewma_log;

	u64			last_bytes;

	u64			avbps;

	u32			last_packets;

	u32			avpps;

	u32			avbps;

	struct rcu_head		e_rcu;

	struct rb_node		node;

};
@@ -115,6 +115,7 @@ static void est_timer(unsigned long arg) 
	rcu_read_lock();

	list_for_each_entry_rcu(e, &elist[idx].list, list) {

		u64 nbytes;

		u64 brate;

		u32 npackets;

		u32 rate;
@@ -125,9 +126,9 @@ static void est_timer(unsigned long arg) 


		nbytes = e->bstats->bytes;

		npackets = e->bstats->packets;

		rate = (nbytes - e->last_bytes)<<(7 - idx);

		brate = (nbytes - e->last_bytes)<<(7 - idx);

		e->last_bytes = nbytes;

		e->avbps += ((long)rate - (long)e->avbps) >> e->ewma_log;

		e->avbps += ((s64)(brate - e->avbps)) >> e->ewma_log;

		e->rate_est->bps = (e->avbps+0xF)>>5;



		rate = (npackets - e->last_packets)<<(12 - idx);