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> |
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.. | ||
cpufreq | ||
acpi-ext.c | ||
acpi.c | ||
asm-offsets.c | ||
brl_emu.c | ||
cyclone.c | ||
efi_stub.S | ||
efi.c | ||
entry.h | ||
entry.S | ||
fsys.S | ||
gate-data.S | ||
gate.lds.S | ||
gate.S | ||
head.S | ||
ia64_ksyms.c | ||
init_task.c | ||
iosapic.c | ||
irq_ia64.c | ||
irq_lsapic.c | ||
irq.c | ||
ivt.S | ||
jprobes.S | ||
kprobes.c | ||
machvec.c | ||
Makefile | ||
mca_asm.S | ||
mca_drv_asm.S | ||
mca_drv.c | ||
mca_drv.h | ||
mca.c | ||
minstate.h | ||
module.c | ||
numa.c | ||
pal.S | ||
palinfo.c | ||
patch.c | ||
perfmon_default_smpl.c | ||
perfmon_generic.h | ||
perfmon_itanium.h | ||
perfmon_mckinley.h | ||
perfmon.c | ||
process.c | ||
ptrace.c | ||
sal.c | ||
salinfo.c | ||
semaphore.c | ||
setup.c | ||
sigframe.h | ||
signal.c | ||
smp.c | ||
smpboot.c | ||
sys_ia64.c | ||
time.c | ||
topology.c | ||
traps.c | ||
unaligned.c | ||
uncached.c | ||
unwind_decoder.c | ||
unwind_i.h | ||
unwind.c | ||
vmlinux.lds.S |