mirror of https://gitee.com/openkylin/linux.git
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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| .. | ||
| Makefile | ||
| alpha_ksyms.c | ||
| asm-offsets.c | ||
| console.c | ||
| core_apecs.c | ||
| core_cia.c | ||
| core_irongate.c | ||
| core_lca.c | ||
| core_marvel.c | ||
| core_mcpcia.c | ||
| core_polaris.c | ||
| core_t2.c | ||
| core_titan.c | ||
| core_tsunami.c | ||
| core_wildfire.c | ||
| entry.S | ||
| err_common.c | ||
| err_ev6.c | ||
| err_ev7.c | ||
| err_impl.h | ||
| err_marvel.c | ||
| err_titan.c | ||
| es1888.c | ||
| gct.c | ||
| head.S | ||
| init_task.c | ||
| io.c | ||
| irq.c | ||
| irq_alpha.c | ||
| irq_i8259.c | ||
| irq_impl.h | ||
| irq_pyxis.c | ||
| irq_srm.c | ||
| machvec_impl.h | ||
| module.c | ||
| ns87312.c | ||
| osf_sys.c | ||
| pci-noop.c | ||
| pci.c | ||
| pci_impl.h | ||
| pci_iommu.c | ||
| process.c | ||
| proto.h | ||
| ptrace.c | ||
| semaphore.c | ||
| setup.c | ||
| signal.c | ||
| smc37c93x.c | ||
| smc37c669.c | ||
| smp.c | ||
| srm_env.c | ||
| srmcons.c | ||
| sys_alcor.c | ||
| sys_cabriolet.c | ||
| sys_dp264.c | ||
| sys_eb64p.c | ||
| sys_eiger.c | ||
| sys_jensen.c | ||
| sys_marvel.c | ||
| sys_miata.c | ||
| sys_mikasa.c | ||
| sys_nautilus.c | ||
| sys_noritake.c | ||
| sys_rawhide.c | ||
| sys_ruffian.c | ||
| sys_rx164.c | ||
| sys_sable.c | ||
| sys_sio.c | ||
| sys_sx164.c | ||
| sys_takara.c | ||
| sys_titan.c | ||
| sys_wildfire.c | ||
| systbls.S | ||
| time.c | ||
| traps.c | ||
| vmlinux.lds.S | ||