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| author | Alexey Dobriyan <adobriyan@gmail.com> | 2017-05-08 15:56:15 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-05-08 17:15:11 -0700 |
| commit | c311c797998c1e70eade463dd60b843da4f1a203 (patch) | |
| tree | cf20c8c1e2305c3cdc8a7e405fb69f0bc38eedb9 /include/linux/cpumask.h | |
| parent | 19659c59af52df22d1b85208a2c37b2d46290541 (diff) | |
| download | lwn-c311c797998c1e70eade463dd60b843da4f1a203.tar.gz lwn-c311c797998c1e70eade463dd60b843da4f1a203.zip | |
cpumask: make "nr_cpumask_bits" unsigned
Bit searching functions accept "unsigned long" indices but
"nr_cpumask_bits" is "int" which is signed, so inevitable sign
extensions occur on x86_64. Those MOVSX are #1 MOVSX bloat by number of
uses across whole kernel.
Change "nr_cpumask_bits" to unsigned, this number can't be negative
after all. It allows to do implicit zero-extension on x86_64 without
MOVSX.
Change signed comparisons into unsigned comparisons where necessary.
Other uses looks fine because it is either argument passed to a function
or comparison is already unsigned.
Net win on allyesconfig type of kernel: ~2.8 KB (!)
add/remove: 0/0 grow/shrink: 8/725 up/down: 93/-2926 (-2833)
function old new delta
xen_exit_mmap 691 735 +44
qstat_read 426 440 +14
__cpufreq_cooling_register 1678 1687 +9
trace_rb_cpu_prepare 447 455 +8
vermagic 54 60 +6
nfp_driver_version 54 60 +6
rcu_torture_stats_print 1147 1151 +4
find_next_push_cpu 267 269 +2
xen_irq_resume 961 960 -1
...
init_vp_index 946 906 -40
od_set_powersave_bias 328 281 -47
power_cpu_exit 193 139 -54
arch_show_interrupts 3538 3484 -54
select_idle_sibling 1558 1471 -87
Total: Before=158358910, After=158356077, chg -0.00%
Same arguments apply to "nr_cpu_ids" but I haven't yet found enough
courage to delve into this issue (and proper fix may require new type
"cpu_t" which is whole separate story).
Link: http://lkml.kernel.org/r/20170309205322.GA1728@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.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 | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h index 1a675604b17d..2404ad238c0b 100644 --- a/include/linux/cpumask.h +++ b/include/linux/cpumask.h @@ -40,9 +40,9 @@ extern int nr_cpu_ids; #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 nr_cpu_ids +#define nr_cpumask_bits ((unsigned int)nr_cpu_ids) #else -#define nr_cpumask_bits NR_CPUS +#define nr_cpumask_bits ((unsigned int)NR_CPUS) #endif /* |