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![]() 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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.. | ||
dispatcher | ||
events | ||
executer | ||
hardware | ||
namespace | ||
parser | ||
resources | ||
sleep | ||
tables | ||
utilities | ||
ac.c | ||
acpi_memhotplug.c | ||
asus_acpi.c | ||
battery.c | ||
blacklist.c | ||
bus.c | ||
button.c | ||
container.c | ||
debug.c | ||
ec.c | ||
event.c | ||
fan.c | ||
glue.c | ||
hotkey.c | ||
ibm_acpi.c | ||
Kconfig | ||
Makefile | ||
motherboard.c | ||
numa.c | ||
osl.c | ||
pci_bind.c | ||
pci_irq.c | ||
pci_link.c | ||
pci_root.c | ||
power.c | ||
processor_core.c | ||
processor_idle.c | ||
processor_perflib.c | ||
processor_thermal.c | ||
processor_throttling.c | ||
scan.c | ||
system.c | ||
tables.c | ||
thermal.c | ||
toshiba_acpi.c | ||
utils.c | ||
video.c |