net_sched: add 64bit rate estimators

struct gnet_stats_rate_est contains u32 fields, so the bytes per second
field can wrap at 34360Mbit.

Add a new gnet_stats_rate_est64 structure to get 64bit bps/pps fields,
and switch the kernel to use this structure natively.

This structure is dumped to user space as a new attribute :

TCA_STATS_RATE_EST64

Old tc command will now display the capped bps (to 34360Mbit), instead
of wrapped values, and updated tc command will display correct
information.

Old tc command output, after patch :

eric:~# tc -s -d qd sh dev lo
qdisc pfifo 8001: root refcnt 2 limit 1000p
 Sent 80868245400 bytes 1978837 pkt (dropped 0, overlimits 0 requeues 0)
 rate 34360Mbit 189696pps backlog 0b 0p requeues 0

This patch carefully reorganizes "struct Qdisc" layout to get optimal
performance on SMP.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 17 insertions, 5 deletions

diff --git a/net/core/gen_stats.c b/net/core/gen_stats.c
index ddedf211e588..9d3d9e78397b 100644
--- a/net/core/gen_stats.c
+++ b/net/core/gen_stats.c
@@ -143,18 +143,30 @@ EXPORT_SYMBOL(gnet_stats_copy_basic);
 int
 gnet_stats_copy_rate_est(struct gnet_dump *d,
                          const struct gnet_stats_basic_packed *b,
-                         struct gnet_stats_rate_est *r)
+                         struct gnet_stats_rate_est64 *r)
 {
+        struct gnet_stats_rate_est est;
+        int res;
+
         if (b && !gen_estimator_active(b, r))
                 return 0;
 
+        est.bps = min_t(u64, UINT_MAX, r->bps);
+        /* we have some time before reaching 2^32 packets per second */
+        est.pps = r->pps;
+
         if (d->compat_tc_stats) {
-                d->tc_stats.bps = r->bps;
-                d->tc_stats.pps = r->pps;
+                d->tc_stats.bps = est.bps;
+                d->tc_stats.pps = est.pps;
         }
 
-        if (d->tail)
-                return gnet_stats_copy(d, TCA_STATS_RATE_EST, r, sizeof(*r));
+        if (d->tail) {
+                res = gnet_stats_copy(d, TCA_STATS_RATE_EST, &est, sizeof(est));
+                if (res < 0 || est.bps == r->bps)
+                        return res;
+                /* emit 64bit stats only if needed */
+                return gnet_stats_copy(d, TCA_STATS_RATE_EST64, r, sizeof(*r));
+        }
 
         return 0;
 }