From ca4ec90b31d1ecf01087c607933cf792057bc8bf Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 13 Jun 2013 07:58:30 -0700 Subject: [PATCH] htb: reorder struct htb_class fields for performance 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 Cc: Tom Herbert Signed-off-by: David S. Miller --- 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 1a3655a606c1..7954e73d118a 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 { -- 2.30.2