The patch titled
Subject: cpumask: make "nr_cpumask_bits" unsigned
has been added to the -mm tree. Its filename is
cpumask-make-nr_cpumask_bits-unsigned.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/cpumask-make-nr_cpumask_bits-unsigned.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/cpumask-make-nr_cpumask_bits-unsigned.patch
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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
/*
_
Patches currently in -mm which might be from adobriyan@xxxxxxxxx are
cpumask-make-nr_cpumask_bits-unsigned.patch
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