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Date: Wed, 5 Jan 2022 15:21:39 +0200
From: Vladimir Oltean <vladimir.oltean@....com>
To: netdev@...r.kernel.org
Cc: "David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>, Andrew Lunn <andrew@...n.ch>,
Vivien Didelot <vivien.didelot@...il.com>,
Florian Fainelli <f.fainelli@...il.com>
Subject: [PATCH v2 net-next 5/7] net: dsa: make dsa_switch :: num_ports an unsigned int
Currently, num_ports is declared as size_t, which is defined as
__kernel_ulong_t, therefore it occupies 8 bytes of memory.
Even switches with port numbers in the range of tens are exotic, so
there is no need for this amount of storage.
Additionally, because the max_num_bridges member right above it is also
4 bytes, it means the compiler needs to add padding between the last 2
fields. By reducing the size, we don't need that padding and can reduce
the struct size.
Before:
pahole -C dsa_switch net/dsa/slave.o
struct dsa_switch {
struct device * dev; /* 0 8 */
struct dsa_switch_tree * dst; /* 8 8 */
unsigned int index; /* 16 4 */
u32 setup:1; /* 20: 0 4 */
u32 vlan_filtering_is_global:1; /* 20: 1 4 */
u32 needs_standalone_vlan_filtering:1; /* 20: 2 4 */
u32 configure_vlan_while_not_filtering:1; /* 20: 3 4 */
u32 untag_bridge_pvid:1; /* 20: 4 4 */
u32 assisted_learning_on_cpu_port:1; /* 20: 5 4 */
u32 vlan_filtering:1; /* 20: 6 4 */
u32 pcs_poll:1; /* 20: 7 4 */
u32 mtu_enforcement_ingress:1; /* 20: 8 4 */
/* XXX 23 bits hole, try to pack */
struct notifier_block nb; /* 24 24 */
/* XXX last struct has 4 bytes of padding */
void * priv; /* 48 8 */
void * tagger_data; /* 56 8 */
/* --- cacheline 1 boundary (64 bytes) --- */
struct dsa_chip_data * cd; /* 64 8 */
const struct dsa_switch_ops * ops; /* 72 8 */
u32 phys_mii_mask; /* 80 4 */
/* XXX 4 bytes hole, try to pack */
struct mii_bus * slave_mii_bus; /* 88 8 */
unsigned int ageing_time_min; /* 96 4 */
unsigned int ageing_time_max; /* 100 4 */
struct dsa_8021q_context * tag_8021q_ctx; /* 104 8 */
struct devlink * devlink; /* 112 8 */
unsigned int num_tx_queues; /* 120 4 */
unsigned int num_lag_ids; /* 124 4 */
/* --- cacheline 2 boundary (128 bytes) --- */
unsigned int max_num_bridges; /* 128 4 */
/* XXX 4 bytes hole, try to pack */
size_t num_ports; /* 136 8 */
/* size: 144, cachelines: 3, members: 27 */
/* sum members: 132, holes: 2, sum holes: 8 */
/* sum bitfield members: 9 bits, bit holes: 1, sum bit holes: 23 bits */
/* paddings: 1, sum paddings: 4 */
/* last cacheline: 16 bytes */
};
After:
pahole -C dsa_switch net/dsa/slave.o
struct dsa_switch {
struct device * dev; /* 0 8 */
struct dsa_switch_tree * dst; /* 8 8 */
unsigned int index; /* 16 4 */
u32 setup:1; /* 20: 0 4 */
u32 vlan_filtering_is_global:1; /* 20: 1 4 */
u32 needs_standalone_vlan_filtering:1; /* 20: 2 4 */
u32 configure_vlan_while_not_filtering:1; /* 20: 3 4 */
u32 untag_bridge_pvid:1; /* 20: 4 4 */
u32 assisted_learning_on_cpu_port:1; /* 20: 5 4 */
u32 vlan_filtering:1; /* 20: 6 4 */
u32 pcs_poll:1; /* 20: 7 4 */
u32 mtu_enforcement_ingress:1; /* 20: 8 4 */
/* XXX 23 bits hole, try to pack */
struct notifier_block nb; /* 24 24 */
/* XXX last struct has 4 bytes of padding */
void * priv; /* 48 8 */
void * tagger_data; /* 56 8 */
/* --- cacheline 1 boundary (64 bytes) --- */
struct dsa_chip_data * cd; /* 64 8 */
const struct dsa_switch_ops * ops; /* 72 8 */
u32 phys_mii_mask; /* 80 4 */
/* XXX 4 bytes hole, try to pack */
struct mii_bus * slave_mii_bus; /* 88 8 */
unsigned int ageing_time_min; /* 96 4 */
unsigned int ageing_time_max; /* 100 4 */
struct dsa_8021q_context * tag_8021q_ctx; /* 104 8 */
struct devlink * devlink; /* 112 8 */
unsigned int num_tx_queues; /* 120 4 */
unsigned int num_lag_ids; /* 124 4 */
/* --- cacheline 2 boundary (128 bytes) --- */
unsigned int max_num_bridges; /* 128 4 */
unsigned int num_ports; /* 132 4 */
/* size: 136, cachelines: 3, members: 27 */
/* sum members: 128, holes: 1, sum holes: 4 */
/* sum bitfield members: 9 bits, bit holes: 1, sum bit holes: 23 bits */
/* paddings: 1, sum paddings: 4 */
/* last cacheline: 8 bytes */
};
Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
---
include/net/dsa.h | 2 +-
net/dsa/dsa2.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/include/net/dsa.h b/include/net/dsa.h
index a8a586039033..fef9d8bb5190 100644
--- a/include/net/dsa.h
+++ b/include/net/dsa.h
@@ -435,7 +435,7 @@ struct dsa_switch {
*/
unsigned int max_num_bridges;
- size_t num_ports;
+ unsigned int num_ports;
};
static inline struct dsa_port *dsa_to_port(struct dsa_switch *ds, int p)
diff --git a/net/dsa/dsa2.c b/net/dsa/dsa2.c
index c1da813786a4..3d21521453fe 100644
--- a/net/dsa/dsa2.c
+++ b/net/dsa/dsa2.c
@@ -1475,7 +1475,7 @@ static int dsa_switch_parse_ports_of(struct dsa_switch *ds,
}
if (reg >= ds->num_ports) {
- dev_err(ds->dev, "port %pOF index %u exceeds num_ports (%zu)\n",
+ dev_err(ds->dev, "port %pOF index %u exceeds num_ports (%u)\n",
port, reg, ds->num_ports);
of_node_put(port);
err = -EINVAL;
--
2.25.1
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