Excerpts from Christophe Leroy's message of January 14, 2021 12:50 am:

Le 13/01/2021 à 08:32, Nicholas Piggin a écrit :

quoted

Add context tracking to the system call handler explicitly, and remove
_TIF_NOHZ.

This saves 35 cycles on gettid system call cost on POWER9 with a
CONFIG_NOHZ_FULL kernel.

35 cycles among 100 cycles, or among 5000 cycles ? I meant what pourcentage to you win ?

I can re-check when I update and retest. On the order of about 500
IIRC, so quite significant proportion of the cost.

Thanks,
Nick