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| author | zenghongling <zenghongling@kylinos.cn> | 2026-05-11 10:03:09 +0300 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2026-06-03 01:22:13 +0300 |
| commit | 7201b96495522c9ed6fcd9a6b95c08e96c6b3df8 (patch) | |
| tree | a10c16b5ba9f58c0f461ea8ced9ab644dc16a6f3 /include/linux/timerqueue.h | |
| parent | d52c1331d28f7a1ae1255cb64d652e86431e6a03 (diff) | |
| download | linux-7201b96495522c9ed6fcd9a6b95c08e96c6b3df8.tar.xz | |
mm/percpu-internal.h: optimise pcpu_chunk struct to save memory
Using pahole, we can see that there are some padding holes in the current
pcpu_chunk structure,Adjusting the layout of pcpu_chunk can reduce these
holes,decreasing its size from 192 bytes to 128 bytes and eliminating a
wasted cache line.
With allmodconfig (CONFIG_PERCPU_STATS + NEED_PCPUOBJ_EXT)
Before:
/* size: 256, cachelines: 4, members: 19 */
After:
/* size: 192, cachelines: 3, members: 19 */
with NEED_PCPUOBJ_EXT
Before:
struct pcpu_chunk {
struct list_head list; /* 0 16 */
int free_bytes; /* 16 4 */
struct pcpu_block_md chunk_md; /* 20 32 */
/* XXX 4 bytes hole, try to pack */
long unsigned int * bound_map; /* 56 8 */
/* --- cacheline 1 boundary (64 bytes) --- */
void * base_addr __attribute__((__aligned__(64))); /* 64 8 */
long unsigned int * alloc_map; /* 72 8 */
struct pcpu_block_md * md_blocks; /* 80 8 */
void * data; /* 88 8 */
bool immutable; /* 96 1 */
bool isolated; /* 97 1 */
/* XXX 2 bytes hole, try to pack */
int start_offset; /* 100 4 */
int end_offset; /* 104 4 */
/* XXX 4 bytes hole, try to pack */
struct obj_cgroup * * obj_cgroups; /* 112 8 */
int nr_pages; /* 120 4 */
int nr_populated; /* 124 4 */
/* --- cacheline 2 boundary (128 bytes) --- */
int nr_empty_pop_pages; /* 128 4 */
/* XXX 4 bytes hole, try to pack */
long unsigned int populated[]; /* 136 0 */
/* size: 192, cachelines: 3, members: 17 */
/* sum members: 122, holes: 4, sum holes: 14 */
/* padding: 56 */
/* forced alignments: 1 */
} __attribute__((__aligned__(64)));
After:
struct pcpu_chunk {
struct list_head list; /* 0 16 */
int free_bytes; /* 16 4 */
struct pcpu_block_md chunk_md; /* 20 32 */
/* XXX 4 bytes hole, try to pack */
long unsigned int * bound_map; /* 56 8 */
/* --- cacheline 1 boundary (64 bytes) --- */
void * base_addr __attribute__((__aligned__(64))); /* 64 8 */
long unsigned int * alloc_map; /* 72 8 */
struct pcpu_block_md * md_blocks; /* 80 8 */
void * data; /* 88 8 */
bool immutable; /* 96 1 */
bool isolated; /* 97 1 */
/* XXX 2 bytes hole, try to pack */
int start_offset; /* 100 4 */
int end_offset; /* 104 4 */
int nr_pages; /* 108 4 */
int nr_populated; /* 112 4 */
int nr_empty_pop_pages; /* 116 4 */
struct obj_cgroup * * obj_cgroups; /* 120 8 */
/* --- cacheline 2 boundary (128 bytes) --- */
long unsigned int populated[]; /* 128 0 */
/* size: 128, cachelines: 2, members: 17 */
/* sum members: 122, holes: 2, sum holes: 6 */
/* forced alignments: 1 */
} __attribute__((__aligned__(64)));
Link: https://lore.kernel.org/20260511070309.44044-1-zenghongling@kylinos.cn
Signed-off-by: zenghongling <zenghongling@kylinos.cn>
Suggested-by: Dennis Zhou <dennis@kernel.org>
Acked-by: Dennis Zhou <dennis@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'include/linux/timerqueue.h')
0 files changed, 0 insertions, 0 deletions