Message ID | 1620890438-9127-1-git-send-email-anshuman.khandual@arm.com (mailing list archive) |
---|---|
State | New, archived |
Headers | show |
Series | [RFC] mm/thp: Update mm's MM_ANONPAGES stat in set_huge_zero_page() | expand |
On 13 May 2021, at 3:20, Anshuman Khandual wrote: > Although the zero huge page is being shared across various processes, each > mapping needs to update its mm's MM_ANONPAGES stat by HPAGE_PMD_NR in order > to be consistent. This just updates the stats in set_huge_zero_page() after > the mapping gets created. In addition, MM_ANONPAGES stats should be decreased at zap_huge_pmd() and __split_huge_pmd_locked() when the zero huge page mapping is removed from a process, right? > > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Zi Yan <ziy@nvidia.com> > Cc: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org > Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> > --- > Should it update MM_SHMEM_PAGES instead ? Applies on latest mainline. zero huge page is added via do_huge_pmd_anonymous_page(), I think MM_ANONPAGES is appropriate. > > mm/huge_memory.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 63ed6b25deaa..262703304807 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -706,6 +706,7 @@ static void set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, > if (pgtable) > pgtable_trans_huge_deposit(mm, pmd, pgtable); > set_pmd_at(mm, haddr, pmd, entry); > + add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); > mm_inc_nr_ptes(mm); > } > > -- > 2.20.1 — Best Regards, Yan Zi
On Thu, May 13, 2021 at 12:20 AM Anshuman Khandual <anshuman.khandual@arm.com> wrote: > > Although the zero huge page is being shared across various processes, each > mapping needs to update its mm's MM_ANONPAGES stat by HPAGE_PMD_NR in order > to be consistent. This just updates the stats in set_huge_zero_page() after > the mapping gets created. I don't get why MM_ANONPAGES needs to be inc'ed when huge zero page is installed. This may cause inconsistency between some counters, for example, MM_ANONPAGES may be much bigger than anon LRU. MM_ANONPAGES should not be inc'ed unless a new page is allocated and installed, right? > > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Zi Yan <ziy@nvidia.com> > Cc: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org > Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> > --- > Should it update MM_SHMEM_PAGES instead ? Applies on latest mainline. > > mm/huge_memory.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 63ed6b25deaa..262703304807 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -706,6 +706,7 @@ static void set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, > if (pgtable) > pgtable_trans_huge_deposit(mm, pmd, pgtable); > set_pmd_at(mm, haddr, pmd, entry); > + add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); > mm_inc_nr_ptes(mm); > } > > -- > 2.20.1 > >
On Thu, May 13, 2021 at 9:50 AM Yang Shi <shy828301@gmail.com> wrote: > > On Thu, May 13, 2021 at 12:20 AM Anshuman Khandual > <anshuman.khandual@arm.com> wrote: > > > > Although the zero huge page is being shared across various processes, each > > mapping needs to update its mm's MM_ANONPAGES stat by HPAGE_PMD_NR in order > > to be consistent. This just updates the stats in set_huge_zero_page() after > > the mapping gets created. > > I don't get why MM_ANONPAGES needs to be inc'ed when huge zero page is > installed. This may cause inconsistency between some counters, for > example, MM_ANONPAGES may be much bigger than anon LRU. > > MM_ANONPAGES should not be inc'ed unless a new page is allocated and > installed, right? I just realized I mixed MM_ANONPAGES up with the global anon pages counter. Take back my comment. Sorry for the confusion. > > > > > Cc: Andrew Morton <akpm@linux-foundation.org> > > Cc: Zi Yan <ziy@nvidia.com> > > Cc: linux-mm@kvack.org > > Cc: linux-kernel@vger.kernel.org > > Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> > > --- > > Should it update MM_SHMEM_PAGES instead ? Applies on latest mainline. > > > > mm/huge_memory.c | 1 + > > 1 file changed, 1 insertion(+) > > > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > > index 63ed6b25deaa..262703304807 100644 > > --- a/mm/huge_memory.c > > +++ b/mm/huge_memory.c > > @@ -706,6 +706,7 @@ static void set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, > > if (pgtable) > > pgtable_trans_huge_deposit(mm, pmd, pgtable); > > set_pmd_at(mm, haddr, pmd, entry); > > + add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); > > mm_inc_nr_ptes(mm); > > } > > > > -- > > 2.20.1 > > > >
On 5/13/21 7:42 PM, Zi Yan wrote: > On 13 May 2021, at 3:20, Anshuman Khandual wrote: > >> Although the zero huge page is being shared across various processes, each >> mapping needs to update its mm's MM_ANONPAGES stat by HPAGE_PMD_NR in order >> to be consistent. This just updates the stats in set_huge_zero_page() after >> the mapping gets created. > > In addition, MM_ANONPAGES stats should be decreased at zap_huge_pmd() and Right, would something like this work ? diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 63ed6b2..776984d 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1678,6 +1678,7 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE); } else if (is_huge_zero_pmd(orig_pmd)) { zap_deposited_table(tlb->mm, pmd); + add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); spin_unlock(ptl); tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE); } else { > __split_huge_pmd_locked() when the zero huge page mapping is removed from > a process, right? __split_huge_pmd_locked() calls __split_huge_zero_page_pmd() which will replace a zero huge page with multiple (HPAGE_PMD_NR) zero small pages. Why should MM_ANONPAGES stats change for the MM when the mapping is still out there but in normal pages now. > >> >> Cc: Andrew Morton <akpm@linux-foundation.org> >> Cc: Zi Yan <ziy@nvidia.com> >> Cc: linux-mm@kvack.org >> Cc: linux-kernel@vger.kernel.org >> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> >> --- >> Should it update MM_SHMEM_PAGES instead ? Applies on latest mainline. > > zero huge page is added via do_huge_pmd_anonymous_page(), I think MM_ANONPAGES > is appropriate. Okay, sure. > >> >> mm/huge_memory.c | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >> index 63ed6b25deaa..262703304807 100644 >> --- a/mm/huge_memory.c >> +++ b/mm/huge_memory.c >> @@ -706,6 +706,7 @@ static void set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, >> if (pgtable) >> pgtable_trans_huge_deposit(mm, pmd, pgtable); >> set_pmd_at(mm, haddr, pmd, entry); >> + add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); >> mm_inc_nr_ptes(mm); >> } >> >> -- >> 2.20.1 > > > — > Best Regards, > Yan Zi >
On 16 May 2021, at 23:51, Anshuman Khandual wrote: > On 5/13/21 7:42 PM, Zi Yan wrote: >> On 13 May 2021, at 3:20, Anshuman Khandual wrote: >> >>> Although the zero huge page is being shared across various processes, each >>> mapping needs to update its mm's MM_ANONPAGES stat by HPAGE_PMD_NR in order >>> to be consistent. This just updates the stats in set_huge_zero_page() after >>> the mapping gets created. >> >> In addition, MM_ANONPAGES stats should be decreased at zap_huge_pmd() and > > Right, would something like this work ? > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 63ed6b2..776984d 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -1678,6 +1678,7 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, > tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE); > } else if (is_huge_zero_pmd(orig_pmd)) { > zap_deposited_table(tlb->mm, pmd); > + add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); > spin_unlock(ptl); > tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE); > } else { > LGTM. >> __split_huge_pmd_locked() when the zero huge page mapping is removed from >> a process, right? > > __split_huge_pmd_locked() calls __split_huge_zero_page_pmd() which will > replace a zero huge page with multiple (HPAGE_PMD_NR) zero small pages. > Why should MM_ANONPAGES stats change for the MM when the mapping is still > out there but in normal pages now. Ah, you are right. I missed this part. No need to change __split_huge_pmd_locked(). >> >>> >>> Cc: Andrew Morton <akpm@linux-foundation.org> >>> Cc: Zi Yan <ziy@nvidia.com> >>> Cc: linux-mm@kvack.org >>> Cc: linux-kernel@vger.kernel.org >>> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> >>> --- >>> Should it update MM_SHMEM_PAGES instead ? Applies on latest mainline. >> >> zero huge page is added via do_huge_pmd_anonymous_page(), I think MM_ANONPAGES >> is appropriate. > > Okay, sure. > >> >>> >>> mm/huge_memory.c | 1 + >>> 1 file changed, 1 insertion(+) >>> >>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >>> index 63ed6b25deaa..262703304807 100644 >>> --- a/mm/huge_memory.c >>> +++ b/mm/huge_memory.c >>> @@ -706,6 +706,7 @@ static void set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, >>> if (pgtable) >>> pgtable_trans_huge_deposit(mm, pmd, pgtable); >>> set_pmd_at(mm, haddr, pmd, entry); >>> + add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); >>> mm_inc_nr_ptes(mm); >>> } >>> >>> -- >>> 2.20.1 >> >> >> — >> Best Regards, >> Yan Zi >> — Best Regards, Yan, Zi
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 63ed6b25deaa..262703304807 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -706,6 +706,7 @@ static void set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, if (pgtable) pgtable_trans_huge_deposit(mm, pmd, pgtable); set_pmd_at(mm, haddr, pmd, entry); + add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); mm_inc_nr_ptes(mm); }
Although the zero huge page is being shared across various processes, each mapping needs to update its mm's MM_ANONPAGES stat by HPAGE_PMD_NR in order to be consistent. This just updates the stats in set_huge_zero_page() after the mapping gets created. Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Zi Yan <ziy@nvidia.com> Cc: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> --- Should it update MM_SHMEM_PAGES instead ? Applies on latest mainline. mm/huge_memory.c | 1 + 1 file changed, 1 insertion(+)