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net: drop_monitor: make last_rx timestamp private 

It was recently pointed out to me that the last_rx field of the
net_device structure wasn't updated regularly.  In fact only the
bonding driver really uses it currently.  Since the drop_monitor code
relies on the last_rx field to detect drops on recevie in hardware, We
need to find a more reliable way to rate limit our drop checks (so
that we don't check for drops on every frame recevied, which would be
inefficient.  This patch makes a last_rx timestamp that is private to
the drop monitor code and is updated for every device that we track.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Neil Horman 2009-09-02 14:37:45 -07:00 committed by David S. Miller
parent 3f968de276
commit 5848cc096a
1 changed files with 12 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
net/core/drop_monitor.c
View File

@ -52,6 +52,7 @@ struct per_cpu_dm_data {
struct dm_hw_stat_delta {
struct net_device *dev;
unsigned long last_rx;
struct list_head list;
struct rcu_head rcu;
unsigned long last_drop_val;
@ -180,18 +181,25 @@ static void trace_napi_poll_hit(struct napi_struct *napi)
struct dm_hw_stat_delta *new_stat;
/*
* Ratelimit our check time to dm_hw_check_delta jiffies
* Don't check napi structures with no associated device
*/
if (!napi->dev ||
!time_after(jiffies, napi->dev->last_rx + dm_hw_check_delta))
if (!napi->dev)
return;
rcu_read_lock();
list_for_each_entry_rcu(new_stat, &hw_stats_list, list) {
/*
* only add a note to our monitor buffer if:
* 1) this is the dev we received on
* 2) its after the last_rx delta
* 3) our rx_dropped count has gone up
*/
if ((new_stat->dev == napi->dev) &&
(time_after(jiffies, new_stat->last_rx + dm_hw_check_delta)) &&
(napi->dev->stats.rx_dropped != new_stat->last_drop_val)) {
trace_drop_common(NULL, NULL);
new_stat->last_drop_val = napi->dev->stats.rx_dropped;
new_stat->last_rx = jiffies;
break;
}
}
@ -287,6 +295,7 @@ static int dropmon_net_event(struct notifier_block *ev_block,
goto out;
new_stat->dev = dev;
new_stat->last_rx = jiffies;
INIT_RCU_HEAD(&new_stat->rcu);
spin_lock(&trace_state_lock);
list_add_rcu(&new_stat->list, &hw_stats_list);