linux/include/vdso
Andrei Vagin 0898a16a36 lib/vdso: Add unlikely() hint into vdso_read_begin()
Place the branch with no concurrent write before the contended case.

Performance numbers for Intel(R) Core(TM) i5-6300U CPU @ 2.40GHz
(more clock_gettime() cycles - the better):
        | before    | after
-----------------------------------
        | 150252214 | 153242367
        | 150301112 | 153324800
        | 150392773 | 153125401
        | 150373957 | 153399355
        | 150303157 | 153489417
        | 150365237 | 153494270
-----------------------------------
avg     | 150331408 | 153345935
diff %  | 2	    | 0
-----------------------------------
stdev % | 0.3	    | 0.1

Co-developed-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: Andrei Vagin <avagin@gmail.com>
Signed-off-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Link: https://lore.kernel.org/r/20191112012724.250792-2-dima@arista.com
2020-01-14 12:20:47 +01:00
..
datapage.h vdso: Remove superfluous #ifdef __KERNEL__ in vdso/datapage.h 2019-06-26 07:28:09 +02:00
helpers.h lib/vdso: Add unlikely() hint into vdso_read_begin() 2020-01-14 12:20:47 +01:00
vsyscall.h timekeeping: Provide a generic update_vsyscall() implementation 2019-06-22 21:21:06 +02:00