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Date: Tue, 30 Nov 2010 14:12:06 +1100
From: Benjamin Herrenschmidt <benh@...nel.crashing.org>
To: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Andrea Arcangeli <aarcange@...hat.com>,
Avi Kivity <avi@...hat.com>,
Thomas Gleixner <tglx@...utronix.de>,
Rik van Riel <riel@...hat.com>, Ingo Molnar <mingo@...e.hu>,
akpm@...ux-foundation.org,
Linus Torvalds <torvalds@...ux-foundation.org>,
linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
linux-mm@...ck.org, David Miller <davem@...emloft.net>,
Hugh Dickins <hugh.dickins@...cali.co.uk>,
Mel Gorman <mel@....ul.ie>, Nick Piggin <npiggin@...nel.dk>,
Paul McKenney <paulmck@...ux.vnet.ibm.com>,
Yanmin Zhang <yanmin_zhang@...ux.intel.com>,
Stephen Rothwell <sfr@...b.auug.org.au>
Subject: Re: [PATCH 09/21] powerpc: Preemptible mmu_gather
On Fri, 2010-11-26 at 15:38 +0100, Peter Zijlstra wrote:
> plain text document attachment (mm-preempt-tlb-gather-power.patch)
> Fix up powerpc to the new mmu_gather stuffs.
>
> PPC has an extra batching queue to RCU free the actual pagetable
> allocations, use the ARCH extentions for that for now.
>
> For the ppc64_tlb_batch, which tracks the vaddrs to unhash from the
> hardware hash-table, keep using per-cpu arrays but flush on context
> switch and use a TLF bit to track the laxy_mmu state.
This breaks embedded 64-bit build. Replace CONFIG_PPC64 with
CONFIG_PPC_BOOK3S_64 to only hit server when you access the
ppc64_tlb_batch in process.c since it doesn't exist for BOOK3E.
This patch to fold into yours fixes it for me:
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 253475b..56ab103 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -393,7 +393,7 @@ struct task_struct *__switch_to(struct task_struct *prev,
struct thread_struct *new_thread, *old_thread;
unsigned long flags;
struct task_struct *last;
-#ifdef CONFIG_PPC64
+#ifdef CONFIG_PPC_BOOK3S_64
struct ppc64_tlb_batch *batch;
#endif
@@ -514,7 +514,9 @@ struct task_struct *__switch_to(struct task_struct *prev,
old_thread->accum_tb += (current_tb - start_tb);
new_thread->start_tb = current_tb;
}
+#endif /* CONFIG_PPC64 */
+#ifdef CONFIG_PPC_BOOK3S_64
batch = &__get_cpu_var(ppc64_tlb_batch);
if (batch->active) {
current_thread_info()->local_flags |= _TLF_LAZY_MMU;
@@ -522,7 +524,7 @@ struct task_struct *__switch_to(struct task_struct *prev,
__flush_tlb_pending(batch);
batch->active = 0;
}
-#endif /* CONFIG_PPC64 */
+#endif /* CONFIG_PPC_BOOK3S_64 */
local_irq_save(flags);
@@ -537,13 +539,13 @@ struct task_struct *__switch_to(struct task_struct *prev,
hard_irq_disable();
last = _switch(old_thread, new_thread);
-#ifdef CONFIG_PPC64
+#ifdef CONFIG_PPC_BOOK3S_64
if (current_thread_info()->local_flags & _TLF_LAZY_MMU) {
current_thread_info()->local_flags &= ~_TLF_LAZY_MMU;
batch = &__get_cpu_var(ppc64_tlb_batch);
batch->active = 1;
}
-#endif /* CONFIG_PPC64 */
+#endif /* CONFIG_PPC_BOOK3S_64 */
local_irq_restore(flags);
Cheers,
Ben.
> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> ---
> arch/powerpc/include/asm/pgalloc.h | 4 ++--
> arch/powerpc/include/asm/thread_info.h | 2 ++
> arch/powerpc/include/asm/tlb.h | 10 ++++++++++
> arch/powerpc/kernel/process.c | 21 ++++++++++++++++++++-
> arch/powerpc/mm/pgtable.c | 14 ++++----------
> arch/powerpc/mm/tlb_hash32.c | 2 +-
> arch/powerpc/mm/tlb_hash64.c | 12 +++++++-----
> arch/powerpc/mm/tlb_nohash.c | 2 +-
> 8 files changed, 47 insertions(+), 20 deletions(-)
>
> Index: linux-2.6/arch/powerpc/include/asm/tlb.h
> ===================================================================
> --- linux-2.6.orig/arch/powerpc/include/asm/tlb.h
> +++ linux-2.6/arch/powerpc/include/asm/tlb.h
> @@ -28,6 +28,16 @@
> #define tlb_start_vma(tlb, vma) do { } while (0)
> #define tlb_end_vma(tlb, vma) do { } while (0)
>
> +#define HAVE_ARCH_MMU_GATHER 1
> +
> +struct pte_freelist_batch;
> +
> +struct arch_mmu_gather {
> + struct pte_freelist_batch *batch;
> +};
> +
> +#define ARCH_MMU_GATHER_INIT (struct arch_mmu_gather){ .batch = NULL, }
> +
> extern void tlb_flush(struct mmu_gather *tlb);
>
> /* Get the generic bits... */
> Index: linux-2.6/arch/powerpc/kernel/process.c
> ===================================================================
> --- linux-2.6.orig/arch/powerpc/kernel/process.c
> +++ linux-2.6/arch/powerpc/kernel/process.c
> @@ -393,6 +393,9 @@ struct task_struct *__switch_to(struct t
> struct thread_struct *new_thread, *old_thread;
> unsigned long flags;
> struct task_struct *last;
> +#ifdef CONFIG_PPC64
> + struct ppc64_tlb_batch *batch;
> +#endif
>
> #ifdef CONFIG_SMP
> /* avoid complexity of lazy save/restore of fpu
> @@ -511,7 +514,15 @@ struct task_struct *__switch_to(struct t
> old_thread->accum_tb += (current_tb - start_tb);
> new_thread->start_tb = current_tb;
> }
> -#endif
> +
> + batch = &__get_cpu_var(ppc64_tlb_batch);
> + if (batch->active) {
> + current_thread_info()->local_flags |= _TLF_LAZY_MMU;
> + if (batch->index)
> + __flush_tlb_pending(batch);
> + batch->active = 0;
> + }
> +#endif /* CONFIG_PPC64 */
>
> local_irq_save(flags);
>
> @@ -527,6 +538,14 @@ struct task_struct *__switch_to(struct t
> hard_irq_disable();
> last = _switch(old_thread, new_thread);
>
> +#ifdef CONFIG_PPC64
> + if (current_thread_info()->local_flags & _TLF_LAZY_MMU) {
> + current_thread_info()->local_flags &= ~_TLF_LAZY_MMU;
> + batch = &__get_cpu_var(ppc64_tlb_batch);
> + batch->active = 1;
> + }
> +#endif /* CONFIG_PPC64 */
> +
> local_irq_restore(flags);
>
> return last;
> Index: linux-2.6/arch/powerpc/mm/pgtable.c
> ===================================================================
> --- linux-2.6.orig/arch/powerpc/mm/pgtable.c
> +++ linux-2.6/arch/powerpc/mm/pgtable.c
> @@ -33,8 +33,6 @@
>
> #include "mmu_decl.h"
>
> -DEFINE_PER_CPU(struct mmu_gather, mmu_gathers);
> -
> #ifdef CONFIG_SMP
>
> /*
> @@ -43,7 +41,6 @@ DEFINE_PER_CPU(struct mmu_gather, mmu_ga
> * freeing a page table page that is being walked without locks
> */
>
> -static DEFINE_PER_CPU(struct pte_freelist_batch *, pte_freelist_cur);
> static unsigned long pte_freelist_forced_free;
>
> struct pte_freelist_batch
> @@ -97,12 +94,10 @@ static void pte_free_submit(struct pte_f
>
> void pgtable_free_tlb(struct mmu_gather *tlb, void *table, unsigned shift)
> {
> - /* This is safe since tlb_gather_mmu has disabled preemption */
> - struct pte_freelist_batch **batchp = &__get_cpu_var(pte_freelist_cur);
> + struct pte_freelist_batch **batchp = &tlb->arch.batch;
> unsigned long pgf;
>
> - if (atomic_read(&tlb->mm->mm_users) < 2 ||
> - cpumask_equal(mm_cpumask(tlb->mm), cpumask_of(smp_processor_id()))){
> + if (atomic_read(&tlb->mm->mm_users) < 2) {
> pgtable_free(table, shift);
> return;
> }
> @@ -124,10 +119,9 @@ void pgtable_free_tlb(struct mmu_gather
> }
> }
>
> -void pte_free_finish(void)
> +void pte_free_finish(struct mmu_gather *tlb)
> {
> - /* This is safe since tlb_gather_mmu has disabled preemption */
> - struct pte_freelist_batch **batchp = &__get_cpu_var(pte_freelist_cur);
> + struct pte_freelist_batch **batchp = &tlb->arch.batch;
>
> if (*batchp == NULL)
> return;
> Index: linux-2.6/arch/powerpc/mm/tlb_hash64.c
> ===================================================================
> --- linux-2.6.orig/arch/powerpc/mm/tlb_hash64.c
> +++ linux-2.6/arch/powerpc/mm/tlb_hash64.c
> @@ -38,13 +38,11 @@ DEFINE_PER_CPU(struct ppc64_tlb_batch, p
> * neesd to be flushed. This function will either perform the flush
> * immediately or will batch it up if the current CPU has an active
> * batch on it.
> - *
> - * Must be called from within some kind of spinlock/non-preempt region...
> */
> void hpte_need_flush(struct mm_struct *mm, unsigned long addr,
> pte_t *ptep, unsigned long pte, int huge)
> {
> - struct ppc64_tlb_batch *batch = &__get_cpu_var(ppc64_tlb_batch);
> + struct ppc64_tlb_batch *batch = &get_cpu_var(ppc64_tlb_batch);
> unsigned long vsid, vaddr;
> unsigned int psize;
> int ssize;
> @@ -99,6 +97,7 @@ void hpte_need_flush(struct mm_struct *m
> */
> if (!batch->active) {
> flush_hash_page(vaddr, rpte, psize, ssize, 0);
> + put_cpu_var(ppc64_tlb_batch);
> return;
> }
>
> @@ -127,6 +126,7 @@ void hpte_need_flush(struct mm_struct *m
> batch->index = ++i;
> if (i >= PPC64_TLB_BATCH_NR)
> __flush_tlb_pending(batch);
> + put_cpu_var(ppc64_tlb_batch);
> }
>
> /*
> @@ -155,7 +155,7 @@ void __flush_tlb_pending(struct ppc64_tl
>
> void tlb_flush(struct mmu_gather *tlb)
> {
> - struct ppc64_tlb_batch *tlbbatch = &__get_cpu_var(ppc64_tlb_batch);
> + struct ppc64_tlb_batch *tlbbatch = &get_cpu_var(ppc64_tlb_batch);
>
> /* If there's a TLB batch pending, then we must flush it because the
> * pages are going to be freed and we really don't want to have a CPU
> @@ -164,8 +164,10 @@ void tlb_flush(struct mmu_gather *tlb)
> if (tlbbatch->index)
> __flush_tlb_pending(tlbbatch);
>
> + put_cpu_var(ppc64_tlb_batch);
> +
> /* Push out batch of freed page tables */
> - pte_free_finish();
> + pte_free_finish(tlb);
> }
>
> /**
> Index: linux-2.6/arch/powerpc/include/asm/thread_info.h
> ===================================================================
> --- linux-2.6.orig/arch/powerpc/include/asm/thread_info.h
> +++ linux-2.6/arch/powerpc/include/asm/thread_info.h
> @@ -139,10 +139,12 @@ static inline struct thread_info *curren
> #define TLF_NAPPING 0 /* idle thread enabled NAP mode */
> #define TLF_SLEEPING 1 /* suspend code enabled SLEEP mode */
> #define TLF_RESTORE_SIGMASK 2 /* Restore signal mask in do_signal */
> +#define TLF_LAZY_MMU 3 /* tlb_batch is active */
>
> #define _TLF_NAPPING (1 << TLF_NAPPING)
> #define _TLF_SLEEPING (1 << TLF_SLEEPING)
> #define _TLF_RESTORE_SIGMASK (1 << TLF_RESTORE_SIGMASK)
> +#define _TLF_LAZY_MMU (1 << TLF_LAZY_MMU)
>
> #ifndef __ASSEMBLY__
> #define HAVE_SET_RESTORE_SIGMASK 1
> Index: linux-2.6/arch/powerpc/include/asm/pgalloc.h
> ===================================================================
> --- linux-2.6.orig/arch/powerpc/include/asm/pgalloc.h
> +++ linux-2.6/arch/powerpc/include/asm/pgalloc.h
> @@ -32,13 +32,13 @@ static inline void pte_free(struct mm_st
>
> #ifdef CONFIG_SMP
> extern void pgtable_free_tlb(struct mmu_gather *tlb, void *table, unsigned shift);
> -extern void pte_free_finish(void);
> +extern void pte_free_finish(struct mmu_gather *tlb);
> #else /* CONFIG_SMP */
> static inline void pgtable_free_tlb(struct mmu_gather *tlb, void *table, unsigned shift)
> {
> pgtable_free(table, shift);
> }
> -static inline void pte_free_finish(void) { }
> +static inline void pte_free_finish(struct mmu_gather *tlb) { }
> #endif /* !CONFIG_SMP */
>
> static inline void __pte_free_tlb(struct mmu_gather *tlb, struct page *ptepage,
> Index: linux-2.6/arch/powerpc/mm/tlb_hash32.c
> ===================================================================
> --- linux-2.6.orig/arch/powerpc/mm/tlb_hash32.c
> +++ linux-2.6/arch/powerpc/mm/tlb_hash32.c
> @@ -73,7 +73,7 @@ void tlb_flush(struct mmu_gather *tlb)
> }
>
> /* Push out batch of freed page tables */
> - pte_free_finish();
> + pte_free_finish(tlb);
> }
>
> /*
> Index: linux-2.6/arch/powerpc/mm/tlb_nohash.c
> ===================================================================
> --- linux-2.6.orig/arch/powerpc/mm/tlb_nohash.c
> +++ linux-2.6/arch/powerpc/mm/tlb_nohash.c
> @@ -301,7 +301,7 @@ void tlb_flush(struct mmu_gather *tlb)
> flush_tlb_mm(tlb->mm);
>
> /* Push out batch of freed page tables */
> - pte_free_finish();
> + pte_free_finish(tlb);
> }
>
> /*
>
>
> --
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