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Date: Wed, 20 Sep 2023 20:17:12 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>
Cc: Willem de Bruijn <willemb@...gle.com>, Soheil Hassas Yeganeh <soheil@...gle.com>,
Neal Cardwell <ncardwell@...gle.com>, Jamal Hadi Salim <jhs@...atatu.com>,
Cong Wang <xiyou.wangcong@...il.com>, Jiri Pirko <jiri@...nulli.us>, netdev@...r.kernel.org,
eric.dumazet@...il.com, Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH v2 net-next 2/5] net_sched: sch_fq: struct sched_data reorg
q->flows can be often modified, and q->timer_slack is read mostly.
Exchange the two fields, so that cache line countaining
quantum, initial_quantum, and other critical parameters
stay clean (read-mostly).
Move q->watchdog next to q->stat_throttled
Add comments explaining how the structure is split in
three different parts.
pahole output before the patch:
struct fq_sched_data {
struct fq_flow_head new_flows; /* 0 0x10 */
struct fq_flow_head old_flows; /* 0x10 0x10 */
struct rb_root delayed; /* 0x20 0x8 */
u64 time_next_delayed_flow; /* 0x28 0x8 */
u64 ktime_cache; /* 0x30 0x8 */
unsigned long unthrottle_latency_ns; /* 0x38 0x8 */
/* --- cacheline 1 boundary (64 bytes) --- */
struct fq_flow internal __attribute__((__aligned__(64))); /* 0x40 0x80 */
/* XXX last struct has 16 bytes of padding */
/* --- cacheline 3 boundary (192 bytes) --- */
u32 quantum; /* 0xc0 0x4 */
u32 initial_quantum; /* 0xc4 0x4 */
u32 flow_refill_delay; /* 0xc8 0x4 */
u32 flow_plimit; /* 0xcc 0x4 */
unsigned long flow_max_rate; /* 0xd0 0x8 */
u64 ce_threshold; /* 0xd8 0x8 */
u64 horizon; /* 0xe0 0x8 */
u32 orphan_mask; /* 0xe8 0x4 */
u32 low_rate_threshold; /* 0xec 0x4 */
struct rb_root * fq_root; /* 0xf0 0x8 */
u8 rate_enable; /* 0xf8 0x1 */
u8 fq_trees_log; /* 0xf9 0x1 */
u8 horizon_drop; /* 0xfa 0x1 */
/* XXX 1 byte hole, try to pack */
<bad> u32 flows; /* 0xfc 0x4 */
/* --- cacheline 4 boundary (256 bytes) --- */
u32 inactive_flows; /* 0x100 0x4 */
u32 throttled_flows; /* 0x104 0x4 */
u64 stat_gc_flows; /* 0x108 0x8 */
u64 stat_internal_packets; /* 0x110 0x8 */
u64 stat_throttled; /* 0x118 0x8 */
u64 stat_ce_mark; /* 0x120 0x8 */
u64 stat_horizon_drops; /* 0x128 0x8 */
u64 stat_horizon_caps; /* 0x130 0x8 */
u64 stat_flows_plimit; /* 0x138 0x8 */
/* --- cacheline 5 boundary (320 bytes) --- */
u64 stat_pkts_too_long; /* 0x140 0x8 */
u64 stat_allocation_errors; /* 0x148 0x8 */
<bad> u32 timer_slack; /* 0x150 0x4 */
/* XXX 4 bytes hole, try to pack */
struct qdisc_watchdog watchdog; /* 0x158 0x48 */
/* size: 448, cachelines: 7, members: 34 */
/* sum members: 411, holes: 2, sum holes: 5 */
/* padding: 32 */
/* paddings: 1, sum paddings: 16 */
/* forced alignments: 1 */
};
pahole output after the patch:
struct fq_sched_data {
struct fq_flow_head new_flows; /* 0 0x10 */
struct fq_flow_head old_flows; /* 0x10 0x10 */
struct rb_root delayed; /* 0x20 0x8 */
u64 time_next_delayed_flow; /* 0x28 0x8 */
u64 ktime_cache; /* 0x30 0x8 */
unsigned long unthrottle_latency_ns; /* 0x38 0x8 */
/* --- cacheline 1 boundary (64 bytes) --- */
struct fq_flow internal __attribute__((__aligned__(64))); /* 0x40 0x80 */
/* XXX last struct has 16 bytes of padding */
/* --- cacheline 3 boundary (192 bytes) --- */
u32 quantum; /* 0xc0 0x4 */
u32 initial_quantum; /* 0xc4 0x4 */
u32 flow_refill_delay; /* 0xc8 0x4 */
u32 flow_plimit; /* 0xcc 0x4 */
unsigned long flow_max_rate; /* 0xd0 0x8 */
u64 ce_threshold; /* 0xd8 0x8 */
u64 horizon; /* 0xe0 0x8 */
u32 orphan_mask; /* 0xe8 0x4 */
u32 low_rate_threshold; /* 0xec 0x4 */
struct rb_root * fq_root; /* 0xf0 0x8 */
u8 rate_enable; /* 0xf8 0x1 */
u8 fq_trees_log; /* 0xf9 0x1 */
u8 horizon_drop; /* 0xfa 0x1 */
/* XXX 1 byte hole, try to pack */
<good> u32 timer_slack; /* 0xfc 0x4 */
/* --- cacheline 4 boundary (256 bytes) --- */
<good> u32 flows; /* 0x100 0x4 */
u32 inactive_flows; /* 0x104 0x4 */
u32 throttled_flows; /* 0x108 0x4 */
/* XXX 4 bytes hole, try to pack */
u64 stat_throttled; /* 0x110 0x8 */
<better> struct qdisc_watchdog watchdog; /* 0x118 0x48 */
/* --- cacheline 5 boundary (320 bytes) was 32 bytes ago --- */
u64 stat_gc_flows; /* 0x160 0x8 */
u64 stat_internal_packets; /* 0x168 0x8 */
u64 stat_ce_mark; /* 0x170 0x8 */
u64 stat_horizon_drops; /* 0x178 0x8 */
/* --- cacheline 6 boundary (384 bytes) --- */
u64 stat_horizon_caps; /* 0x180 0x8 */
u64 stat_flows_plimit; /* 0x188 0x8 */
u64 stat_pkts_too_long; /* 0x190 0x8 */
u64 stat_allocation_errors; /* 0x198 0x8 */
/* Force padding: */
u64 :64;
u64 :64;
u64 :64;
u64 :64;
/* size: 448, cachelines: 7, members: 34 */
/* sum members: 411, holes: 2, sum holes: 5 */
/* padding: 32 */
/* paddings: 1, sum paddings: 16 */
/* forced alignments: 1 */
};
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
net/sched/sch_fq.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
diff --git a/net/sched/sch_fq.c b/net/sched/sch_fq.c
index f59a2cb2c803d79bd1f0eb1806464a0220824f9e..230300aac3ed1c86c8a52f405a03f67b60848a05 100644
--- a/net/sched/sch_fq.c
+++ b/net/sched/sch_fq.c
@@ -104,6 +104,9 @@ struct fq_sched_data {
unsigned long unthrottle_latency_ns;
struct fq_flow internal; /* for non classified or high prio packets */
+
+/* Read mostly cache line */
+
u32 quantum;
u32 initial_quantum;
u32 flow_refill_delay;
@@ -117,22 +120,27 @@ struct fq_sched_data {
u8 rate_enable;
u8 fq_trees_log;
u8 horizon_drop;
+ u32 timer_slack; /* hrtimer slack in ns */
+
+/* Read/Write fields. */
+
u32 flows;
u32 inactive_flows;
u32 throttled_flows;
+ u64 stat_throttled;
+ struct qdisc_watchdog watchdog;
u64 stat_gc_flows;
+
+/* Seldom used fields. */
+
u64 stat_internal_packets;
- u64 stat_throttled;
u64 stat_ce_mark;
u64 stat_horizon_drops;
u64 stat_horizon_caps;
u64 stat_flows_plimit;
u64 stat_pkts_too_long;
u64 stat_allocation_errors;
-
- u32 timer_slack; /* hrtimer slack in ns */
- struct qdisc_watchdog watchdog;
};
/*
--
2.42.0.459.ge4e396fd5e-goog
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