diff options
| author |   Alexey Dobriyan <adobriyan@gmail.com> | 2017-09-08 16:14:18 -0700 |
|---|---|---|
| committer |   Linus Torvalds <torvalds@linux-foundation.org> | 2017-09-08 18:26:48 -0700 |
| commit | 9b130ad5bb8255ee8534d92d67e12b2a4887eacb (patch) | |
| tree | 125a5e867be6b0dbd4958ca41426e2c733768110 /include/linux/cpumask.h | |
| parent | vga: optimise console scrolling (diff) | |
| download | linux-dev-9b130ad5bb8255ee8534d92d67e12b2a4887eacb.tar.xz linux-dev-9b130ad5bb8255ee8534d92d67e12b2a4887eacb.zip | |
treewide: make "nr_cpu_ids" unsigned
First, number of CPUs can't be negative number.
Second, different signnnedness leads to suboptimal code in the following
cases:
1)
kmalloc(nr_cpu_ids * sizeof(X));
"int" has to be sign extended to size_t.
2)
while (loff_t *pos < nr_cpu_ids)
MOVSXD is 1 byte longed than the same MOV.
Other cases exist as well. Basically compiler is told that nr_cpu_ids
can't be negative which can't be deduced if it is "int".
Code savings on allyesconfig kernel: -3KB
add/remove: 0/0 grow/shrink: 25/264 up/down: 261/-3631 (-3370)
function old new delta
coretemp_cpu_online 450 512 +62
rcu_init_one 1234 1272 +38
pci_device_probe 374 399 +25
...
pgdat_reclaimable_pages 628 556 -72
select_fallback_rq 446 369 -77
task_numa_find_cpu 1923 1807 -116
Link: http://lkml.kernel.org/r/20170819114959.GA30580@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/cpumask.h')
| -rw-r--r-- | include/linux/cpumask.h | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h index 4bf4479a3a80..68c5a8290275 100644 --- a/include/linux/cpumask.h +++ b/include/linux/cpumask.h @@ -32,15 +32,15 @@ typedef struct cpumask { DECLARE_BITMAP(bits, NR_CPUS); } cpumask_t; #define cpumask_pr_args(maskp) nr_cpu_ids, cpumask_bits(maskp) #if NR_CPUS == 1 -#define nr_cpu_ids 1 +#define nr_cpu_ids 1U #else -extern int nr_cpu_ids; +extern unsigned int nr_cpu_ids; #endif #ifdef CONFIG_CPUMASK_OFFSTACK /* Assuming NR_CPUS is huge, a runtime limit is more efficient. Also, * not all bits may be allocated. */ -#define nr_cpumask_bits ((unsigned int)nr_cpu_ids) +#define nr_cpumask_bits nr_cpu_ids #else #define nr_cpumask_bits ((unsigned int)NR_CPUS) #endif |