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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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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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.. | ||
acpi | ||
cpufreq | ||
aperture.c | ||
apic.c | ||
asm-offsets.c | ||
crash.c | ||
e820.c | ||
early_printk.c | ||
entry.S | ||
genapic_cluster.c | ||
genapic_flat.c | ||
genapic.c | ||
head64.c | ||
head.S | ||
i387.c | ||
i8259.c | ||
init_task.c | ||
io_apic.c | ||
ioport.c | ||
irq.c | ||
kprobes.c | ||
ldt.c | ||
machine_kexec.c | ||
Makefile | ||
mce_intel.c | ||
mce.c | ||
module.c | ||
mpparse.c | ||
nmi.c | ||
pci-dma.c | ||
pci-gart.c | ||
pci-nommu.c | ||
pmtimer.c | ||
process.c | ||
ptrace.c | ||
reboot.c | ||
relocate_kernel.S | ||
setup64.c | ||
setup.c | ||
signal.c | ||
smp.c | ||
smpboot.c | ||
suspend_asm.S | ||
suspend.c | ||
sys_x86_64.c | ||
syscall.c | ||
time.c | ||
trampoline.S | ||
traps.c | ||
vmlinux.lds.S | ||
vsyscall.c | ||
x8664_ksyms.c |