mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-04 17:56:45 +07:00
64c7c8f885
Make some changes to the NEED_RESCHED and POLLING_NRFLAG to reduce confusion, and make their semantics rigid. Improves efficiency of resched_task and some cpu_idle routines. * In resched_task: - TIF_NEED_RESCHED is only cleared with the task's runqueue lock held, and as we hold it during resched_task, then there is no need for an atomic test and set there. The only other time this should be set is when the task's quantum expires, in the timer interrupt - this is protected against because the rq lock is irq-safe. - If TIF_NEED_RESCHED is set, then we don't need to do anything. It won't get unset until the task get's schedule()d off. - If we are running on the same CPU as the task we resched, then set TIF_NEED_RESCHED and no further action is required. - If we are running on another CPU, and TIF_POLLING_NRFLAG is *not* set after TIF_NEED_RESCHED has been set, then we need to send an IPI. Using these rules, we are able to remove the test and set operation in resched_task, and make clear the previously vague semantics of POLLING_NRFLAG. * In idle routines: - Enter cpu_idle with preempt disabled. When the need_resched() condition becomes true, explicitly call schedule(). This makes things a bit clearer (IMO), but haven't updated all architectures yet. - Many do a test and clear of TIF_NEED_RESCHED for some reason. According to the resched_task rules, this isn't needed (and actually breaks the assumption that TIF_NEED_RESCHED is only cleared with the runqueue lock held). So remove that. Generally one less locked memory op when switching to the idle thread. - Many idle routines clear TIF_POLLING_NRFLAG, and only set it in the inner most polling idle loops. The above resched_task semantics allow it to be set until before the last time need_resched() is checked before going into a halt requiring interrupt wakeup. Many idle routines simply never enter such a halt, and so POLLING_NRFLAG can be always left set, completely eliminating resched IPIs when rescheduling the idle task. POLLING_NRFLAG width can be increased, to reduce the chance of resched IPIs. Signed-off-by: Nick Piggin <npiggin@suse.de> Cc: Ingo Molnar <mingo@elte.hu> Cc: Con Kolivas <kernel@kolivas.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org> |
||
---|---|---|
.. | ||
apc.c | ||
asm-offsets.c | ||
auxio.c | ||
cpu.c | ||
devices.c | ||
ebus.c | ||
entry.S | ||
errtbls.c | ||
etrap.S | ||
head.S | ||
idprom.c | ||
init_task.c | ||
ioport.c | ||
irq.c | ||
led.c | ||
Makefile | ||
module.c | ||
muldiv.c | ||
pcic.c | ||
pmc.c | ||
process.c | ||
ptrace.c | ||
rtrap.S | ||
sclow.S | ||
semaphore.c | ||
setup.c | ||
signal.c | ||
smp.c | ||
sparc_ksyms.c | ||
sparc-stub.c | ||
sun4c_irq.c | ||
sun4d_irq.c | ||
sun4d_smp.c | ||
sun4m_irq.c | ||
sun4m_smp.c | ||
sun4setup.c | ||
sunos_asm.S | ||
sunos_ioctl.c | ||
sys_solaris.c | ||
sys_sparc.c | ||
sys_sunos.c | ||
systbls.S | ||
tadpole.c | ||
tick14.c | ||
time.c | ||
trampoline.S | ||
traps.c | ||
unaligned.c | ||
vmlinux.lds.S | ||
windows.c | ||
wof.S | ||
wuf.S |