linux-kernel - Re: [RFC 13/20] mm/tlb: introduce tlb_start_ptes() and tlb_end

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Date:   Mon, 1 Feb 2021 07:29:07 +0000
From:   Nadav Amit <namit@...are.com>
To:     Damian Tometzki <damian@...etzki.de>
CC:     Linux-MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will@...nel.org>, Yu Zhao <yuzhao@...gle.com>,
        Nick Piggin <npiggin@...il.com>,
        "x86@...nel.org" <x86@...nel.org>
Subject: Re: [RFC 13/20] mm/tlb: introduce tlb_start_ptes() and tlb_end_ptes()

> On Jan 31, 2021, at 2:07 AM, Damian Tometzki <linux@...etzki.de> wrote:
> 
> On Sat, 30. Jan 16:11, Nadav Amit wrote:
>> From: Nadav Amit <namit@...are.com>
>> 
>> Introduce tlb_start_ptes() and tlb_end_ptes() which would be called
>> before and after PTEs are updated and TLB flushes are deferred. This
>> will be later be used for fine granualrity deferred TLB flushing
>> detection.
>> 
>> In the meanwhile, move flush_tlb_batched_pending() into
>> tlb_start_ptes(). It was not called from mapping_dirty_helpers by
>> wp_pte() and clean_record_pte(), which might be a bug.
>> 
>> No additional functional change is intended.
>> 
>> Signed-off-by: Nadav Amit <namit@...are.com>
>> Cc: Andrea Arcangeli <aarcange@...hat.com>
>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>> Cc: Andy Lutomirski <luto@...nel.org>
>> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
>> Cc: Peter Zijlstra <peterz@...radead.org>
>> Cc: Thomas Gleixner <tglx@...utronix.de>
>> Cc: Will Deacon <will@...nel.org>
>> Cc: Yu Zhao <yuzhao@...gle.com>
>> Cc: Nick Piggin <npiggin@...il.com>
>> Cc: x86@...nel.org
>> ---
>> fs/proc/task_mmu.c         |  2 ++
>> include/asm-generic/tlb.h  | 18 ++++++++++++++++++
>> mm/madvise.c               |  6 ++++--
>> mm/mapping_dirty_helpers.c | 15 +++++++++++++--
>> mm/memory.c                |  2 ++
>> mm/mprotect.c              |  3 ++-
>> 6 files changed, 41 insertions(+), 5 deletions(-)
>> 
>> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
>> index 4cd048ffa0f6..d0cce961fa5c 100644
>> --- a/fs/proc/task_mmu.c
>> +++ b/fs/proc/task_mmu.c
>> @@ -1168,6 +1168,7 @@ static int clear_refs_pte_range(pmd_t *pmd, unsigned long addr,
>> 		return 0;
>> 
>> 	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
>> +	tlb_start_ptes(&cp->tlb);
>> 	for (; addr != end; pte++, addr += PAGE_SIZE) {
>> 		ptent = *pte;
>> 
>> @@ -1190,6 +1191,7 @@ static int clear_refs_pte_range(pmd_t *pmd, unsigned long addr,
>> 		tlb_flush_pte_range(&cp->tlb, addr, PAGE_SIZE);
>> 		ClearPageReferenced(page);
>> 	}
>> +	tlb_end_ptes(&cp->tlb);
>> 	pte_unmap_unlock(pte - 1, ptl);
>> 	cond_resched();
>> 	return 0;
>> diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h
>> index 041be2ef4426..10690763090a 100644
>> --- a/include/asm-generic/tlb.h
>> +++ b/include/asm-generic/tlb.h
>> @@ -58,6 +58,11 @@
>>  *    Defaults to flushing at tlb_end_vma() to reset the range; helps when
>>  *    there's large holes between the VMAs.
>>  *
>> + *  - tlb_start_ptes() / tlb_end_ptes; makr the start / end of PTEs change.
> 
> Hello Nadav,
> 
> short nid makr/mark

Thanks! I will fix it.