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: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 6 deletions

diff --git a/net/core/gen_estimator.c b/net/core/gen_estimator.c
index 9cc9f95b109e..6d62d4618cfc 100644
--- a/net/core/gen_estimator.c
+++ b/net/core/gen_estimator.c
@@ -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);