mainlining shenanigans
7787ff7763
struct dsa_switch has 9 boolean properties, many of which are in fact
set by drivers for custom behavior (vlan_filtering_is_global,
needs_standalone_vlan_filtering, etc etc). The binary layout of the
structure could be improved. For example, the "bool setup" at the
beginning introduces a gratuitous 7 byte hole in the first cache line.
The change merges all boolean properties into bitfields of an u32, and
places that u32 in the first cache line of the structure, since many
bools are accessed from the data path (untag_bridge_pvid, vlan_filtering,
vlan_filtering_is_global).
We place this u32 after the existing ds->index, which is also 4 bytes in
size. As a positive side effect, ds->tagger_data now fits into the first
cache line too, because 4 bytes are saved.
Before:
pahole -C dsa_switch net/dsa/slave.o
struct dsa_switch {
bool setup; /* 0 1 */
/* XXX 7 bytes hole, try to pack */
struct device * dev; /* 8 8 */
struct dsa_switch_tree * dst; /* 16 8 */
unsigned int index; /* 24 4 */
/* XXX 4 bytes hole, try to pack */
struct notifier_block nb; /* 32 24 */
/* XXX last struct has 4 bytes of padding */
void * priv; /* 56 8 */
/* --- cacheline 1 boundary (64 bytes) --- */
void * tagger_data; /* 64 8 */
struct dsa_chip_data * cd; /* 72 8 */
const struct dsa_switch_ops * ops; /* 80 8 */
u32 phys_mii_mask; /* 88 4 */
/* XXX 4 bytes hole, try to pack */
struct mii_bus * slave_mii_bus; /* 96 8 */
unsigned int ageing_time_min; /* 104 4 */
unsigned int ageing_time_max; /* 108 4 */
struct dsa_8021q_context * tag_8021q_ctx; /* 112 8 */
struct devlink * devlink; /* 120 8 */
/* --- cacheline 2 boundary (128 bytes) --- */
unsigned int num_tx_queues; /* 128 4 */
bool vlan_filtering_is_global; /* 132 1 */
bool needs_standalone_vlan_filtering; /* 133 1 */
bool configure_vlan_while_not_filtering; /* 134 1 */
bool untag_bridge_pvid; /* 135 1 */
bool assisted_learning_on_cpu_port; /* 136 1 */
bool vlan_filtering; /* 137 1 */
bool pcs_poll; /* 138 1 */
bool mtu_enforcement_ingress; /* 139 1 */
unsigned int num_lag_ids; /* 140 4 */
unsigned int max_num_bridges; /* 144 4 */
/* XXX 4 bytes hole, try to pack */
size_t num_ports; /* 152 8 */
/* size: 160, cachelines: 3, members: 27 */
/* sum members: 141, holes: 4, sum holes: 19 */
/* paddings: 1, sum paddings: 4 */
/* last cacheline: 32 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 */
/* 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 */
};
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.