From: Alexey Dobriyan <adobriyan@xxxxxxxxx> Subject: 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@xxxxxxxxx> Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx> Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx> Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- arch/mips/kernel/perf_event_mipsxx.c | 2 +- arch/s390/kernel/perf_cpum_sf.c | 2 +- include/linux/cpumask.h | 4 ++-- 3 files changed, 4 insertions(+), 4 deletions(-) diff -puN arch/mips/kernel/perf_event_mipsxx.c~cpumask-make-nr_cpumask_bits-unsigned arch/mips/kernel/perf_event_mipsxx.c --- a/arch/mips/kernel/perf_event_mipsxx.c~cpumask-make-nr_cpumask_bits-unsigned +++ a/arch/mips/kernel/perf_event_mipsxx.c @@ -618,7 +618,7 @@ static int mipspmu_event_init(struct per return -ENOENT; } - if (event->cpu >= nr_cpumask_bits || + if ((unsigned int)event->cpu >= nr_cpumask_bits || (event->cpu >= 0 && !cpu_online(event->cpu))) return -ENODEV; diff -puN arch/s390/kernel/perf_cpum_sf.c~cpumask-make-nr_cpumask_bits-unsigned arch/s390/kernel/perf_cpum_sf.c --- a/arch/s390/kernel/perf_cpum_sf.c~cpumask-make-nr_cpumask_bits-unsigned +++ a/arch/s390/kernel/perf_cpum_sf.c @@ -823,7 +823,7 @@ static int cpumsf_pmu_event_init(struct } /* Check online status of the CPU to which the event is pinned */ - if (event->cpu >= nr_cpumask_bits || + if ((unsigned int)event->cpu >= nr_cpumask_bits || (event->cpu >= 0 && !cpu_online(event->cpu))) return -ENODEV; diff -puN include/linux/cpumask.h~cpumask-make-nr_cpumask_bits-unsigned include/linux/cpumask.h --- a/include/linux/cpumask.h~cpumask-make-nr_cpumask_bits-unsigned +++ a/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 /* _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
