mirror of
https://github.com/torvalds/linux
synced 2024-10-23 03:37:40 +00:00
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> |
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| .. | ||
| cpufreq | ||
| acpi-ext.c | ||
| acpi.c | ||
| asm-offsets.c | ||
| brl_emu.c | ||
| cyclone.c | ||
| efi.c | ||
| efi_stub.S | ||
| 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.c | ||
| irq_ia64.c | ||
| irq_lsapic.c | ||
| ivt.S | ||
| jprobes.S | ||
| kprobes.c | ||
| machvec.c | ||
| Makefile | ||
| mca.c | ||
| mca_asm.S | ||
| mca_drv.c | ||
| mca_drv.h | ||
| mca_drv_asm.S | ||
| minstate.h | ||
| module.c | ||
| numa.c | ||
| pal.S | ||
| palinfo.c | ||
| patch.c | ||
| perfmon.c | ||
| perfmon_default_smpl.c | ||
| perfmon_generic.h | ||
| perfmon_itanium.h | ||
| perfmon_mckinley.h | ||
| 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.c | ||
| unwind_decoder.c | ||
| unwind_i.h | ||
| vmlinux.lds.S | ||