linux-stable/arch/powerpc/include
Christophe Leroy a85c728cb5 powerpc/32: Don't use lmw/stmw for saving/restoring non volatile regs
Instructions lmw/stmw are interesting for functions that are rarely
used and not in the cache, because only one instruction is to be
copied into the instruction cache instead of 19. However those
instruction are less performant than 19x raw lwz/stw as they require
synchronisation plus one additional cycle.

SAVE_NVGPRS / REST_NVGPRS are used in only a few places which are
mostly in interrupts entries/exits and in task switch so they are
likely already in the cache.

Using standard lwz improves null_syscall selftest by:
- 10 cycles on mpc832x.
- 2 cycles on mpc8xx.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/316c543b8906712c108985c8463eec09c8db577b.1629732542.git.christophe.leroy@csgroup.eu
2021-10-22 15:22:04 +11:00
..
asm powerpc/32: Don't use lmw/stmw for saving/restoring non volatile regs 2021-10-22 15:22:04 +11:00
uapi/asm powerpc/perf: Expose instruction and data address registers as part of extended regs 2021-10-12 18:39:02 +11:00