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Date: Tue, 03 Apr 2012 09:55:21 +0400
From: Konstantin Khlebnikov <khlebnikov@...nvz.org>
To: Suresh Siddha <suresh.b.siddha@...el.com>
CC: Konstantin Khlebnikov <koct9i@...il.com>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
Andrew Morton <akpm@...ux-foundation.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Andi Kleen <andi@...stfloor.org>,
Pallipadi Venkatesh <venki@...gle.com>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Nick Piggin <npiggin@...nel.dk>, Nick Piggin <npiggin@...e.de>
Subject: Re: [x86 PAT PATCH 2/2] mm, x86, PAT: rework linear pfn-mmap tracking
Konstantin Khlebnikov wrote:
> Suresh Siddha wrote:
>> From: Konstantin Khlebnikov<khlebnikov@...nvz.org>
>>
>> This patch replaces generic vma-flag VM_PFN_AT_MMAP with x86-only VM_PAT.
>>
>> We can toss mapping address from remap_pfn_range() into track_pfn_vma_new(),
>> and collect all PAT-related logic together in arch/x86/.
>>
>> This patch also restores orignal frustration-free is_cow_mapping() check in
>> remap_pfn_range(), as it was before commit v2.6.28-rc8-88-g3c8bb73
>> ("x86: PAT: store vm_pgoff for all linear_over_vma_region mappings - v3")
>>
>> is_linear_pfn_mapping() checks can be removed from mm/huge_memory.c,
>> because it already handled by VM_PFNMAP in VM_NO_THP bit-mask.
>>
>> Signed-off-by: Konstantin Khlebnikov<khlebnikov@...nvz.org>
>> Signed-off-by: Suresh Siddha<suresh.b.siddha@...el.com>
>> Cc: Venkatesh Pallipadi<venki@...gle.com>
>> Cc: H. Peter Anvin<hpa@...or.com>
>> Cc: Nick Piggin<npiggin@...e.de>
>> Cc: Ingo Molnar<mingo@...hat.com>
>> ---
>> arch/x86/mm/pat.c | 16 +++++++++++-----
>> include/asm-generic/pgtable.h | 4 ++--
>> include/linux/mm.h | 15 +--------------
>> mm/huge_memory.c | 7 +++----
>> mm/memory.c | 15 ++++++++-------
>> 5 files changed, 25 insertions(+), 32 deletions(-)
>>
>> diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
>> index 617f42b..cde7e19 100644
>> --- a/arch/x86/mm/pat.c
>> +++ b/arch/x86/mm/pat.c
>> @@ -665,7 +665,7 @@ int track_pfn_vma_copy(struct vm_area_struct *vma)
>> unsigned long vma_size = vma->vm_end - vma->vm_start;
>> pgprot_t pgprot;
>>
>> - if (is_linear_pfn_mapping(vma)) {
>> + if (vma->vm_flags& VM_PAT) {
>> /*
>> * reserve the whole chunk covered by vma. We need the
>> * starting address and protection from pte.
>> @@ -690,13 +690,19 @@ int track_pfn_vma_copy(struct vm_area_struct *vma)
>> * single reserve_pfn_range call.
>> */
>> int track_pfn_vma_new(struct vm_area_struct *vma, pgprot_t *prot,
>> - unsigned long pfn, unsigned long size)
>> + unsigned long addr, unsigned long pfn, unsigned long size)
>> {
>> unsigned long flags;
>>
>> /* reserve the whole chunk starting from pfn */
>> - if (is_linear_pfn_mapping(vma))
>> - return reserve_pfn_range(pfn, size, prot, 0);
>> + if (addr == vma->vm_start&& size == (vma->vm_end - vma->vm_start)) {
>> + int ret;
>> +
>> + ret = reserve_pfn_range(pfn, size, prot, 0);
>> + if (!ret)
>> + vma->vm_flags |= VM_PAT;
>> + return ret;
>> + }
>>
>> if (!pat_enabled)
>> return 0;
>> @@ -720,7 +726,7 @@ void untrack_pfn_vma(struct vm_area_struct *vma, unsigned long pfn,
>> resource_size_t paddr;
>> unsigned long prot;
>>
>> - if (!is_linear_pfn_mapping(vma))
>> + if (!(vma->vm_flags& VM_PAT))
>> return;
>>
>> /* free the chunk starting from pfn or the whole chunk */
>> diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
>> index 125c54e..688a2a5 100644
>> --- a/include/asm-generic/pgtable.h
>> +++ b/include/asm-generic/pgtable.h
>> @@ -389,7 +389,7 @@ static inline void ptep_modify_prot_commit(struct mm_struct *mm,
>> * for physical range indicated by pfn and size.
>> */
>> static inline int track_pfn_vma_new(struct vm_area_struct *vma, pgprot_t *prot,
>> - unsigned long pfn, unsigned long size)
>> + unsigned long pfn, unsigned long addr, unsigned long size)
>> {
>> return 0;
>> }
>> @@ -420,7 +420,7 @@ static inline void untrack_pfn_vma(struct vm_area_struct *vma,
>> }
>> #else
>> extern int track_pfn_vma_new(struct vm_area_struct *vma, pgprot_t *prot,
>> - unsigned long pfn, unsigned long size);
>> + unsigned long pfn, unsigned long addr, unsigned long size);
>> extern int track_pfn_vma_copy(struct vm_area_struct *vma);
>> extern void untrack_pfn_vma(struct vm_area_struct *vma, unsigned long pfn,
>> unsigned long size);
>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>> index d8738a4..b8e5fe5 100644
>> --- a/include/linux/mm.h
>> +++ b/include/linux/mm.h
>> @@ -117,7 +117,7 @@ extern unsigned int kobjsize(const void *objp);
>> #define VM_CAN_NONLINEAR 0x08000000 /* Has ->fault& does nonlinear pages */
>> #define VM_MIXEDMAP 0x10000000 /* Can contain "struct page" and pure PFN pages */
>> #define VM_SAO 0x20000000 /* Strong Access Ordering (powerpc) */
>> -#define VM_PFN_AT_MMAP 0x40000000 /* PFNMAP vma that is fully mapped at mmap time */
>> +#define VM_PAT 0x40000000 /* PAT reserves whole VMA at once (x86) */
>> #define VM_MERGEABLE 0x80000000 /* KSM may merge identical pages */
>>
>> /* Bits set in the VMA until the stack is in its final location */
>> @@ -158,19 +158,6 @@ extern pgprot_t protection_map[16];
>> #define FAULT_FLAG_RETRY_NOWAIT 0x10 /* Don't drop mmap_sem and wait when retrying */
>> #define FAULT_FLAG_KILLABLE 0x20 /* The fault task is in SIGKILL killable region */
>>
>> -/*
>> - * This interface is used by x86 PAT code to identify a pfn mapping that is
>> - * linear over entire vma. This is to optimize PAT code that deals with
>> - * marking the physical region with a particular prot. This is not for generic
>> - * mm use. Note also that this check will not work if the pfn mapping is
>> - * linear for a vma starting at physical address 0. In which case PAT code
>> - * falls back to slow path of reserving physical range page by page.
>> - */
>> -static inline int is_linear_pfn_mapping(struct vm_area_struct *vma)
>> -{
>> - return !!(vma->vm_flags& VM_PFN_AT_MMAP);
>> -}
>> -
>> static inline int is_pfn_mapping(struct vm_area_struct *vma)
>> {
>> return !!(vma->vm_flags& VM_PFNMAP);
>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>> index f0e5306..cf827da 100644
>> --- a/mm/huge_memory.c
>> +++ b/mm/huge_memory.c
>> @@ -1650,7 +1650,7 @@ int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
>> * If is_pfn_mapping() is true is_learn_pfn_mapping() must be
>> * true too, verify it here.
>> */
>> - VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags& VM_NO_THP);
>> + VM_BUG_ON(vma->vm_flags& VM_NO_THP);
>> hstart = (vma->vm_start + ~HPAGE_PMD_MASK)& HPAGE_PMD_MASK;
>> hend = vma->vm_end& HPAGE_PMD_MASK;
>> if (hstart< hend)
>> @@ -1908,7 +1908,7 @@ static void collapse_huge_page(struct mm_struct *mm,
>> * If is_pfn_mapping() is true is_learn_pfn_mapping() must be
>> * true too, verify it here.
>> */
>> - VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags& VM_NO_THP);
>> + VM_BUG_ON(vma->vm_flags& VM_NO_THP);
>>
>> pgd = pgd_offset(mm, address);
>> if (!pgd_present(*pgd))
>> @@ -2150,8 +2150,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
>> * If is_pfn_mapping() is true is_learn_pfn_mapping()
>> * must be true too, verify it here.
>> */
>> - VM_BUG_ON(is_linear_pfn_mapping(vma) ||
>> - vma->vm_flags& VM_NO_THP);
>> + VM_BUG_ON(vma->vm_flags& VM_NO_THP);
>>
>> hstart = (vma->vm_start + ~HPAGE_PMD_MASK)& HPAGE_PMD_MASK;
>> hend = vma->vm_end& HPAGE_PMD_MASK;
>> diff --git a/mm/memory.c b/mm/memory.c
>> index 6105f47..e6e4dfd 100644
>> --- a/mm/memory.c
>> +++ b/mm/memory.c
>> @@ -2145,7 +2145,7 @@ int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
>>
>> if (addr< vma->vm_start || addr>= vma->vm_end)
>> return -EFAULT;
>> - if (track_pfn_vma_new(vma,&pgprot, pfn, PAGE_SIZE))
>> + if (track_pfn_vma_new(vma,&pgprot, pfn, addr, PAGE_SIZE))
>> return -EINVAL;
>
> Old code does not uses PAT for vm_insert_pfn, now it can use it for single-page vma.
> And I see glitches on my notebook if kernel do this (see comment in v2 of my patch)
>
> Probably we shouldn't touch this, plus seems like using pat-engine for single page isn't optimal:
> it allocates special control structures for this.
Ignore this, I didn't see comment in 0/2 mail
>
>>
>> ret = insert_pfn(vma, addr, pfn, pgprot);
>> @@ -2285,23 +2285,24 @@ int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
>> * There's a horrible special case to handle copy-on-write
>> * behaviour that some programs depend on. We mark the "original"
>> * un-COW'ed pages by matching them up with "vma->vm_pgoff".
>> + * See vm_normal_page() for details.
>> */
>> - if (addr == vma->vm_start&& end == vma->vm_end) {
>> +
>> + if (is_cow_mapping(vma->vm_flags)) {
>> + if (addr != vma->vm_start || end != vma->vm_end)
>> + return -EINVAL;
>> vma->vm_pgoff = pfn;
>> - vma->vm_flags |= VM_PFN_AT_MMAP;
>> - } else if (is_cow_mapping(vma->vm_flags))
>> - return -EINVAL;
>> + }
>>
>> vma->vm_flags |= VM_IO | VM_RESERVED | VM_PFNMAP;
>>
>> - err = track_pfn_vma_new(vma,&prot, pfn, PAGE_ALIGN(size));
>> + err = track_pfn_vma_new(vma,&prot, pfn, addr, PAGE_ALIGN(size));
>> if (err) {
>> /*
>> * To indicate that track_pfn related cleanup is not
>> * needed from higher level routine calling unmap_vmas
>> */
>> vma->vm_flags&= ~(VM_IO | VM_RESERVED | VM_PFNMAP);
>> - vma->vm_flags&= ~VM_PFN_AT_MMAP;
>> return -EINVAL;
>> }
>>
>
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