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Date: Wed, 17 Jul 2013 09:21:00 +0200
From: Ingo Molnar <mingo@...nel.org>
To: Dave Hansen <dave@...1.net>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org, linux-mm@...ck.org,
Andrew Morton <akpm@...ux-foundation.org>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [RESEND][PATCH] mm: vmstats: tlb flush counters
* Dave Hansen <dave@...1.net> wrote:
> I was investigating some TLB flush scaling issues and realized
> that we do not have any good methods for figuring out how many
> TLB flushes we are doing.
>
> It would be nice to be able to do these in generic code, but the
> arch-independent calls don't explicitly specify whether we
> actually need to do remote flushes or not. In the end, we really
> need to know if we actually _did_ global vs. local invalidations,
> so that leaves us with few options other than to muck with the
> counters from arch-specific code.
>
> Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
> ---
>
> linux.git-davehans/arch/x86/mm/tlb.c | 18 ++++++++++++++----
> linux.git-davehans/include/linux/vm_event_item.h | 5 +++++
> linux.git-davehans/mm/vmstat.c | 5 +++++
> 3 files changed, 24 insertions(+), 4 deletions(-)
>
> diff -puN arch/x86/mm/tlb.c~tlb-vmstats arch/x86/mm/tlb.c
> --- linux.git/arch/x86/mm/tlb.c~tlb-vmstats 2013-07-16 16:41:56.476280350 -0700
> +++ linux.git-davehans/arch/x86/mm/tlb.c 2013-07-16 16:41:56.483280658 -0700
> @@ -103,6 +103,7 @@ static void flush_tlb_func(void *info)
> if (f->flush_mm != this_cpu_read(cpu_tlbstate.active_mm))
> return;
>
> + count_vm_event(NR_TLB_REMOTE_FLUSH_RECEIVED);
> if (this_cpu_read(cpu_tlbstate.state) == TLBSTATE_OK) {
> if (f->flush_end == TLB_FLUSH_ALL)
> local_flush_tlb();
> @@ -130,6 +131,7 @@ void native_flush_tlb_others(const struc
> info.flush_start = start;
> info.flush_end = end;
>
> + count_vm_event(NR_TLB_REMOTE_FLUSH);
> if (is_uv_system()) {
> unsigned int cpu;
>
> @@ -149,6 +151,7 @@ void flush_tlb_current_task(void)
>
> preempt_disable();
>
> + count_vm_event(NR_TLB_LOCAL_FLUSH_ALL);
> local_flush_tlb();
> if (cpumask_any_but(mm_cpumask(mm), smp_processor_id()) < nr_cpu_ids)
> flush_tlb_others(mm_cpumask(mm), mm, 0UL, TLB_FLUSH_ALL);
> @@ -211,16 +214,19 @@ void flush_tlb_mm_range(struct mm_struct
> act_entries = mm->total_vm > tlb_entries ? tlb_entries : mm->total_vm;
>
> /* tlb_flushall_shift is on balance point, details in commit log */
> - if ((end - start) >> PAGE_SHIFT > act_entries >> tlb_flushall_shift)
> + if ((end - start) >> PAGE_SHIFT > act_entries >> tlb_flushall_shift) {
> + count_vm_event(NR_TLB_LOCAL_FLUSH_ALL);
> local_flush_tlb();
> - else {
> + } else {
> if (has_large_page(mm, start, end)) {
> local_flush_tlb();
> goto flush_all;
> }
> /* flush range by one by one 'invlpg' */
> - for (addr = start; addr < end; addr += PAGE_SIZE)
> + for (addr = start; addr < end; addr += PAGE_SIZE) {
> + count_vm_event(NR_TLB_LOCAL_FLUSH_ONE);
> __flush_tlb_single(addr);
> + }
>
> if (cpumask_any_but(mm_cpumask(mm),
> smp_processor_id()) < nr_cpu_ids)
> @@ -256,6 +262,7 @@ void flush_tlb_page(struct vm_area_struc
>
> static void do_flush_tlb_all(void *info)
> {
> + count_vm_event(NR_TLB_REMOTE_FLUSH_RECEIVED);
> __flush_tlb_all();
> if (this_cpu_read(cpu_tlbstate.state) == TLBSTATE_LAZY)
> leave_mm(smp_processor_id());
> @@ -263,6 +270,7 @@ static void do_flush_tlb_all(void *info)
>
> void flush_tlb_all(void)
> {
> + count_vm_event(NR_TLB_REMOTE_FLUSH);
> on_each_cpu(do_flush_tlb_all, NULL, 1);
> }
>
> @@ -272,8 +280,10 @@ static void do_kernel_range_flush(void *
> unsigned long addr;
>
> /* flush range by one by one 'invlpg' */
> - for (addr = f->flush_start; addr < f->flush_end; addr += PAGE_SIZE)
> + for (addr = f->flush_start; addr < f->flush_end; addr += PAGE_SIZE) {
> + count_vm_event(NR_TLB_LOCAL_FLUSH_ONE_KERNEL);
> __flush_tlb_single(addr);
> + }
> }
>
> void flush_tlb_kernel_range(unsigned long start, unsigned long end)
> diff -puN include/linux/vm_event_item.h~tlb-vmstats include/linux/vm_event_item.h
> --- linux.git/include/linux/vm_event_item.h~tlb-vmstats 2013-07-16 16:41:56.478280438 -0700
> +++ linux.git-davehans/include/linux/vm_event_item.h 2013-07-16 16:41:56.483280658 -0700
> @@ -70,6 +70,11 @@ enum vm_event_item { PGPGIN, PGPGOUT, PS
> THP_ZERO_PAGE_ALLOC,
> THP_ZERO_PAGE_ALLOC_FAILED,
> #endif
>
> + NR_TLB_REMOTE_FLUSH, /* cpu tried to flush others' tlbs */
> + NR_TLB_REMOTE_FLUSH_RECEIVED,/* cpu received ipi for flush */
> + NR_TLB_LOCAL_FLUSH_ALL,
> + NR_TLB_LOCAL_FLUSH_ONE,
> + NR_TLB_LOCAL_FLUSH_ONE_KERNEL,
Please fix the vertical alignment of comments.
> NR_VM_EVENT_ITEMS
> };
>
> diff -puN mm/vmstat.c~tlb-vmstats mm/vmstat.c
> --- linux.git/mm/vmstat.c~tlb-vmstats 2013-07-16 16:41:56.480280525 -0700
> +++ linux.git-davehans/mm/vmstat.c 2013-07-16 16:41:56.484280703 -0700
> @@ -817,6 +817,11 @@ const char * const vmstat_text[] = {
> "thp_zero_page_alloc",
> "thp_zero_page_alloc_failed",
> #endif
> + "nr_tlb_remote_flush",
> + "nr_tlb_remote_flush_received",
> + "nr_tlb_local_flush_all",
> + "nr_tlb_local_flush_one",
> + "nr_tlb_local_flush_one_kernel",
At first sight this seems pretty x86 specific. No range flush events, etc.
But no strong objections from me, if Andrew likes it.
Thanks,
Ingo
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