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| author | Eric Dumazet <edumazet@google.com> | 2016-12-02 08:11:00 -0800 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2016-12-03 16:12:17 -0500 |
| commit | 12efa1fa43968fcb707e806dc119df499c17ac2c (patch) | |
| tree | 1af0100515470e6aa6a942f0d13ff51529efbc81 /net/core | |
| parent | e01b16a7e217a23eb97e08d0a591735d5aee5efc (diff) | |
| download | linux-12efa1fa43968fcb707e806dc119df499c17ac2c.tar.gz linux-12efa1fa43968fcb707e806dc119df499c17ac2c.tar.bz2 linux-12efa1fa43968fcb707e806dc119df499c17ac2c.zip | |
net_sched: gen_estimator: account for timer drifts
Under heavy stress, timer used in estimators tend to slowly be delayed
by a few jiffies, leading to inaccuracies.
Lets remember what was the last scheduled jiffies so that we get more
precise estimations, without having to add a multiply/divide in the loop
to account for the drifts.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core')
| -rw-r--r-- | net/core/gen_estimator.c | 25 |
1 files changed, 16 insertions, 9 deletions
diff --git a/net/core/gen_estimator.c b/net/core/gen_estimator.c index cad8e791f28e..0993844faeea 100644 --- a/net/core/gen_estimator.c +++ b/net/core/gen_estimator.c @@ -78,8 +78,7 @@ #define EST_MAX_INTERVAL 5 -struct gen_estimator -{ +struct gen_estimator { struct list_head list; struct gnet_stats_basic_packed *bstats; struct gnet_stats_rate_est64 *rate_est; @@ -96,8 +95,8 @@ struct gen_estimator struct rcu_head head; }; -struct gen_estimator_head -{ +struct gen_estimator_head { + unsigned long next_jiffies; struct timer_list timer; struct list_head list; }; @@ -146,8 +145,15 @@ skip: spin_unlock(e->stats_lock); } - if (!list_empty(&elist[idx].list)) - mod_timer(&elist[idx].timer, jiffies + ((HZ/4) << idx)); + if (!list_empty(&elist[idx].list)) { + elist[idx].next_jiffies += ((HZ/4) << idx); + + if (unlikely(time_after_eq(jiffies, elist[idx].next_jiffies))) { + /* Ouch... timer was delayed. */ + elist[idx].next_jiffies = jiffies + 1; + } + mod_timer(&elist[idx].timer, elist[idx].next_jiffies); + } rcu_read_unlock(); } @@ -251,9 +257,10 @@ int gen_new_estimator(struct gnet_stats_basic_packed *bstats, setup_timer(&elist[idx].timer, est_timer, idx); } - if (list_empty(&elist[idx].list)) - mod_timer(&elist[idx].timer, jiffies + ((HZ/4) << idx)); - + if (list_empty(&elist[idx].list)) { + elist[idx].next_jiffies = jiffies + ((HZ/4) << idx); + mod_timer(&elist[idx].timer, elist[idx].next_jiffies); + } list_add_rcu(&est->list, &elist[idx].list); gen_add_node(est); spin_unlock_bh(&est_tree_lock); |