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Date: Thu, 13 Jun 2013 07:58:30 -0700
From: Eric Dumazet <eric.dumazet@...il.com>
To: David Miller <davem@...emloft.net>
Cc: netdev <netdev@...r.kernel.org>, Tom Herbert <therbert@...gle.com>
Subject: [PATCH net-next] htb: reorder struct htb_class fields for
performance
From: Eric Dumazet <edumazet@...gle.com>
htb_class structures are big, and source of false sharing on SMP.
By carefully splitting them in two parts, we can improve performance.
I got 9 % performance increase on a 24 threads machine, with 200
concurrent netperf in TCP_RR mode, using a HTB hierarchy of 4 classes.
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Tom Herbert <therbert@...gle.com>
---
net/sched/sch_htb.c | 62 ++++++++++++++++++++++--------------------
1 file changed, 33 insertions(+), 29 deletions(-)
diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
index 1a3655a..7954e73 100644
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c
@@ -76,23 +76,39 @@ enum htb_cmode {
HTB_CAN_SEND /* class can send */
};
-/* interior & leaf nodes; props specific to leaves are marked L: */
+/* interior & leaf nodes; props specific to leaves are marked L:
+ * To reduce false sharing, place mostly read fields at beginning,
+ * and mostly written ones at the end.
+ */
struct htb_class {
struct Qdisc_class_common common;
- /* general class parameters */
- struct gnet_stats_basic_packed bstats;
- struct gnet_stats_queue qstats;
+ struct psched_ratecfg rate;
+ struct psched_ratecfg ceil;
+ s64 buffer, cbuffer;/* token bucket depth/rate */
+ s64 mbuffer; /* max wait time */
+ int prio; /* these two are used only by leaves... */
+ int quantum; /* but stored for parent-to-leaf return */
+
+ struct tcf_proto *filter_list; /* class attached filters */
+ int filter_cnt;
+ int refcnt; /* usage count of this class */
+
+ int level; /* our level (see above) */
+ unsigned int children;
+ struct htb_class *parent; /* parent class */
+
struct gnet_stats_rate_est64 rate_est;
- struct tc_htb_xstats xstats; /* our special stats */
- int refcnt; /* usage count of this class */
- /* topology */
- int level; /* our level (see above) */
- unsigned int children;
- struct htb_class *parent; /* parent class */
+ /*
+ * Written often fields
+ */
+ struct gnet_stats_basic_packed bstats;
+ struct gnet_stats_queue qstats;
+ struct tc_htb_xstats xstats; /* our special stats */
- int prio; /* these two are used only by leaves... */
- int quantum; /* but stored for parent-to-leaf return */
+ /* token bucket parameters */
+ s64 tokens, ctokens;/* current number of tokens */
+ s64 t_c; /* checkpoint time */
union {
struct htb_class_leaf {
@@ -111,24 +127,12 @@ struct htb_class {
u32 last_ptr_id[TC_HTB_NUMPRIO];
} inner;
} un;
- struct rb_node node[TC_HTB_NUMPRIO]; /* node for self or feed tree */
- struct rb_node pq_node; /* node for event queue */
- s64 pq_key;
-
- int prio_activity; /* for which prios are we active */
- enum htb_cmode cmode; /* current mode of the class */
+ s64 pq_key;
- /* class attached filters */
- struct tcf_proto *filter_list;
- int filter_cnt;
-
- /* token bucket parameters */
- struct psched_ratecfg rate;
- struct psched_ratecfg ceil;
- s64 buffer, cbuffer; /* token bucket depth/rate */
- s64 mbuffer; /* max wait time */
- s64 tokens, ctokens; /* current number of tokens */
- s64 t_c; /* checkpoint time */
+ int prio_activity; /* for which prios are we active */
+ enum htb_cmode cmode; /* current mode of the class */
+ struct rb_node pq_node; /* node for event queue */
+ struct rb_node node[TC_HTB_NUMPRIO]; /* node for self or feed tree */
};
struct htb_sched {
--
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