Messages in this thread | | | Subject | Re: [PATCH, RFC] improved hacks to allow -rt to run kernbench on POWER | From | Benjamin Herrenschmidt <> | Date | Sat, 10 Nov 2007 07:52:04 +1100 |
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> diff -urpNa -X dontdiff linux-2.6.23.1-rt4/arch/powerpc/kernel/process.c linux-2.6.23.1-rt4-fix/arch/powerpc/kernel/process.c > --- linux-2.6.23.1-rt4/arch/powerpc/kernel/process.c 2007-10-12 09:43:44.000000000 -0700 > +++ linux-2.6.23.1-rt4-fix/arch/powerpc/kernel/process.c 2007-11-08 20:33:59.000000000 -0800 > @@ -245,6 +245,8 @@ struct task_struct *__switch_to(struct t > struct thread_struct *new_thread, *old_thread; > unsigned long flags; > struct task_struct *last; > + struct ppc64_tlb_batch *batch; > + int hadbatch; > > #ifdef CONFIG_SMP > /* avoid complexity of lazy save/restore of fpu > @@ -325,6 +327,16 @@ struct task_struct *__switch_to(struct t > } > #endif > > + batch = &get_cpu_var(ppc64_tlb_batch); > + if (batch->active) { > + hadbatch = 1; > + if (batch->index) { > + __flush_tlb_pending(batch); > + } > + batch->active = 0; > + } > + put_cpu_var(ppc64_tlb_batch); > + > local_irq_save(flags); > > account_system_vtime(current); > @@ -335,6 +347,12 @@ struct task_struct *__switch_to(struct t > > local_irq_restore(flags); > > + if (hadbatch) { > + batch = &get_cpu_var(ppc64_tlb_batch); > + batch->active = 1; > + put_cpu_var(ppc64_tlb_batch); > + } > + > return last; > }
I doubt we can schedule within __switch_to() (can somebody confirm this ?), in which case, you can just use __get_cpu_var() and avoid the put, thus saving a handful of cycles in the code above.
> /* export that to outside world */ > struct device_node *of_chosen; > diff -urpNa -X dontdiff linux-2.6.23.1-rt4/arch/powerpc/mm/fault.c linux-2.6.23.1-rt4-fix/arch/powerpc/mm/fault.c > --- linux-2.6.23.1-rt4/arch/powerpc/mm/fault.c 2007-10-27 22:20:57.000000000 -0700 > +++ linux-2.6.23.1-rt4-fix/arch/powerpc/mm/fault.c 2007-10-28 13:49:07.000000000 -0700 > @@ -301,6 +301,7 @@ good_area: > if (get_pteptr(mm, address, &ptep, &pmdp)) { > spinlock_t *ptl = pte_lockptr(mm, pmdp); > spin_lock(ptl); > + preempt_disable(); > if (pte_present(*ptep)) { > struct page *page = pte_page(*ptep); > > @@ -310,10 +311,12 @@ good_area: > } > pte_update(ptep, 0, _PAGE_HWEXEC); > _tlbie(address); > + preempt_enable(); > pte_unmap_unlock(ptep, ptl); > up_read(&mm->mmap_sem); > return 0; > } > + preempt_enable(); > pte_unmap_unlock(ptep, ptl); > } > #endif
The patch above will have to be rebased following a fix I did that makes _tlbie() takes a context ID argument. I don't actually think preempt_disable/enable is necessary here. I don't think it matters if we preempt here, but I suppose better safe than sorry.... (this is 44x code).
Overall, looks fine !
Cheers, Ben.
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