| Message ID | 20220426144412.742113-2-zokeefe@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm: userspace hugepage collapse | expand |
Hi, Zach, On Tue, Apr 26, 2022 at 07:44:01AM -0700, Zach O'Keefe wrote: > When scanning an anon pmd to see if it's eligible for collapse, return > SCAN_PMD_MAPPED if the pmd already maps a THP. Note that > SCAN_PMD_MAPPED is different from SCAN_PAGE_COMPOUND used in the > file-collapse path, since the latter might identify pte-mapped compound > pages. This is required by MADV_COLLAPSE which necessarily needs to > know what hugepage-aligned/sized regions are already pmd-mapped. > > Signed-off-by: Zach O'Keefe <zokeefe@google.com> > Reported-by: kernel test robot <lkp@intel.com> IIUC we don't need to attach this reported-by if this is not a bugfix. I think you can simply fix all issues reported by the test bot and only attach the line if the patch is fixing the problem that the bot was reporting explicitly. > --- > include/trace/events/huge_memory.h | 3 ++- > mm/internal.h | 1 + > mm/khugepaged.c | 30 ++++++++++++++++++++++++++---- > mm/rmap.c | 15 +++++++++++++-- > 4 files changed, 42 insertions(+), 7 deletions(-) > > diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h > index d651f3437367..9faa678e0a5b 100644 > --- a/include/trace/events/huge_memory.h > +++ b/include/trace/events/huge_memory.h > @@ -33,7 +33,8 @@ > EM( SCAN_ALLOC_HUGE_PAGE_FAIL, "alloc_huge_page_failed") \ > EM( SCAN_CGROUP_CHARGE_FAIL, "ccgroup_charge_failed") \ > EM( SCAN_TRUNCATED, "truncated") \ > - EMe(SCAN_PAGE_HAS_PRIVATE, "page_has_private") \ > + EM( SCAN_PAGE_HAS_PRIVATE, "page_has_private") \ > + EMe(SCAN_PMD_MAPPED, "page_pmd_mapped") \ Nit: IMHO it can be put even in the middle so we don't need to touch the EMe() every time. :) Apart from that, it does sound proper to me to put SCAN_PMD_MAPPED to be right after SCAN_PMD_NULL anyway. > > #undef EM > #undef EMe > diff --git a/mm/internal.h b/mm/internal.h > index 0667abd57634..51ae9f71a2a3 100644 > --- a/mm/internal.h > +++ b/mm/internal.h > @@ -172,6 +172,7 @@ extern void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason > /* > * in mm/rmap.c: > */ > +pmd_t *mm_find_pmd_raw(struct mm_struct *mm, unsigned long address); > extern pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address); > > /* > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index ba8dbd1825da..2933b13fc975 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -51,6 +51,7 @@ enum scan_result { > SCAN_CGROUP_CHARGE_FAIL, > SCAN_TRUNCATED, > SCAN_PAGE_HAS_PRIVATE, > + SCAN_PMD_MAPPED, > }; > > #define CREATE_TRACE_POINTS > @@ -987,6 +988,29 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address, > return 0; > } > > +static int find_pmd_or_thp_or_none(struct mm_struct *mm, > + unsigned long address, > + pmd_t **pmd) > +{ > + pmd_t pmde; > + > + *pmd = mm_find_pmd_raw(mm, address); > + if (!*pmd) > + return SCAN_PMD_NULL; > + > + pmde = pmd_read_atomic(*pmd); > + > +#ifdef CONFIG_TRANSPARENT_HUGEPAGE > + /* See comments in pmd_none_or_trans_huge_or_clear_bad() */ > + barrier(); > +#endif > + if (!pmd_present(pmde) || pmd_none(pmde)) Could we drop the pmd_none() check? I assume !pmd_present() should have covered that case already? > + return SCAN_PMD_NULL; > + if (pmd_trans_huge(pmde)) > + return SCAN_PMD_MAPPED; > + return SCAN_SUCCEED; > +} > + > /* > * Bring missing pages in from swap, to complete THP collapse. > * Only done if khugepaged_scan_pmd believes it is worthwhile. > @@ -1238,11 +1262,9 @@ static int khugepaged_scan_pmd(struct mm_struct *mm, > > VM_BUG_ON(address & ~HPAGE_PMD_MASK); > > - pmd = mm_find_pmd(mm, address); > - if (!pmd) { > - result = SCAN_PMD_NULL; > + result = find_pmd_or_thp_or_none(mm, address, &pmd); > + if (result != SCAN_SUCCEED) > goto out; > - } > > memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); > pte = pte_offset_map_lock(mm, pmd, address, &ptl); > diff --git a/mm/rmap.c b/mm/rmap.c > index 61e63db5dc6f..49817f35e65c 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -759,13 +759,12 @@ unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma) > return vma_address(page, vma); > } > > -pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address) > +pmd_t *mm_find_pmd_raw(struct mm_struct *mm, unsigned long address) > { > pgd_t *pgd; > p4d_t *p4d; > pud_t *pud; > pmd_t *pmd = NULL; > - pmd_t pmde; > > pgd = pgd_offset(mm, address); > if (!pgd_present(*pgd)) > @@ -780,6 +779,18 @@ pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address) > goto out; > > pmd = pmd_offset(pud, address); > +out: > + return pmd; > +} > + > +pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address) > +{ > + pmd_t pmde; > + pmd_t *pmd; > + > + pmd = mm_find_pmd_raw(mm, address); > + if (!pmd) > + goto out; > /* > * Some THP functions use the sequence pmdp_huge_clear_flush(), set_pmd_at() > * without holding anon_vma lock for write. So when looking for a > -- > 2.36.0.rc2.479.g8af0fa9b8e-goog >
Thanks for taking the time to review, Peter! On Tue, Apr 26, 2022 at 5:26 PM Peter Xu <peterx@redhat.com> wrote: > > Hi, Zach, > > On Tue, Apr 26, 2022 at 07:44:01AM -0700, Zach O'Keefe wrote: > > When scanning an anon pmd to see if it's eligible for collapse, return > > SCAN_PMD_MAPPED if the pmd already maps a THP. Note that > > SCAN_PMD_MAPPED is different from SCAN_PAGE_COMPOUND used in the > > file-collapse path, since the latter might identify pte-mapped compound > > pages. This is required by MADV_COLLAPSE which necessarily needs to > > know what hugepage-aligned/sized regions are already pmd-mapped. > > > > Signed-off-by: Zach O'Keefe <zokeefe@google.com> > > Reported-by: kernel test robot <lkp@intel.com> > > IIUC we don't need to attach this reported-by if this is not a bugfix. I > think you can simply fix all issues reported by the test bot and only > attach the line if the patch is fixing the problem that the bot was > reporting explicitly. > Ya, I wasn't entirely sure what to do here, but including seems to not be without precedent, e.g. commit 92bbef67d459 ("mm: make alloc_contig_range work at pageblock granularity"), and likewise just wanted to give credit where I thought it was due. Though, I suppose folks who catch bugs in the review process aren't ack'd similarly, so perhaps it does make sense to remove this. > > --- > > include/trace/events/huge_memory.h | 3 ++- > > mm/internal.h | 1 + > > mm/khugepaged.c | 30 ++++++++++++++++++++++++++---- > > mm/rmap.c | 15 +++++++++++++-- > > 4 files changed, 42 insertions(+), 7 deletions(-) > > > > diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h > > index d651f3437367..9faa678e0a5b 100644 > > --- a/include/trace/events/huge_memory.h > > +++ b/include/trace/events/huge_memory.h > > @@ -33,7 +33,8 @@ > > EM( SCAN_ALLOC_HUGE_PAGE_FAIL, "alloc_huge_page_failed") \ > > EM( SCAN_CGROUP_CHARGE_FAIL, "ccgroup_charge_failed") \ > > EM( SCAN_TRUNCATED, "truncated") \ > > - EMe(SCAN_PAGE_HAS_PRIVATE, "page_has_private") \ > > + EM( SCAN_PAGE_HAS_PRIVATE, "page_has_private") \ > > + EMe(SCAN_PMD_MAPPED, "page_pmd_mapped") \ > > Nit: IMHO it can be put even in the middle so we don't need to touch the > EMe() every time. :) > > Apart from that, it does sound proper to me to put SCAN_PMD_MAPPED to be > right after SCAN_PMD_NULL anyway. > Makes sense to me. Done. > > > > #undef EM > > #undef EMe > > diff --git a/mm/internal.h b/mm/internal.h > > index 0667abd57634..51ae9f71a2a3 100644 > > --- a/mm/internal.h > > +++ b/mm/internal.h > > @@ -172,6 +172,7 @@ extern void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason > > /* > > * in mm/rmap.c: > > */ > > +pmd_t *mm_find_pmd_raw(struct mm_struct *mm, unsigned long address); > > extern pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address); > > > > /* > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > > index ba8dbd1825da..2933b13fc975 100644 > > --- a/mm/khugepaged.c > > +++ b/mm/khugepaged.c > > @@ -51,6 +51,7 @@ enum scan_result { > > SCAN_CGROUP_CHARGE_FAIL, > > SCAN_TRUNCATED, > > SCAN_PAGE_HAS_PRIVATE, > > + SCAN_PMD_MAPPED, > > }; > > > > #define CREATE_TRACE_POINTS > > @@ -987,6 +988,29 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address, > > return 0; > > } > > > > +static int find_pmd_or_thp_or_none(struct mm_struct *mm, > > + unsigned long address, > > + pmd_t **pmd) > > +{ > > + pmd_t pmde; > > + > > + *pmd = mm_find_pmd_raw(mm, address); > > + if (!*pmd) > > + return SCAN_PMD_NULL; > > + > > + pmde = pmd_read_atomic(*pmd); > > + > > +#ifdef CONFIG_TRANSPARENT_HUGEPAGE > > + /* See comments in pmd_none_or_trans_huge_or_clear_bad() */ > > + barrier(); > > +#endif > > + if (!pmd_present(pmde) || pmd_none(pmde)) > > Could we drop the pmd_none() check? I assume !pmd_present() should have > covered that case already? > I opted for safety here since I didn't know if pmd_present() always implied !pmd_none() on all archs, but given mm_find_pmd() elides the check, perhaps it's safe to do so here. Thanks for the suggestion. > > + return SCAN_PMD_NULL; > > + if (pmd_trans_huge(pmde)) > > + return SCAN_PMD_MAPPED; > > + return SCAN_SUCCEED; > > +} > > + > > /* > > * Bring missing pages in from swap, to complete THP collapse. > > * Only done if khugepaged_scan_pmd believes it is worthwhile. > > @@ -1238,11 +1262,9 @@ static int khugepaged_scan_pmd(struct mm_struct *mm, > > > > VM_BUG_ON(address & ~HPAGE_PMD_MASK); > > > > - pmd = mm_find_pmd(mm, address); > > - if (!pmd) { > > - result = SCAN_PMD_NULL; > > + result = find_pmd_or_thp_or_none(mm, address, &pmd); > > + if (result != SCAN_SUCCEED) > > goto out; > > - } > > > > memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); > > pte = pte_offset_map_lock(mm, pmd, address, &ptl); > > diff --git a/mm/rmap.c b/mm/rmap.c > > index 61e63db5dc6f..49817f35e65c 100644 > > --- a/mm/rmap.c > > +++ b/mm/rmap.c > > @@ -759,13 +759,12 @@ unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma) > > return vma_address(page, vma); > > } > > > > -pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address) > > +pmd_t *mm_find_pmd_raw(struct mm_struct *mm, unsigned long address) > > { > > pgd_t *pgd; > > p4d_t *p4d; > > pud_t *pud; > > pmd_t *pmd = NULL; > > - pmd_t pmde; > > > > pgd = pgd_offset(mm, address); > > if (!pgd_present(*pgd)) > > @@ -780,6 +779,18 @@ pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address) > > goto out; > > > > pmd = pmd_offset(pud, address); > > +out: > > + return pmd; > > +} > > + > > +pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address) > > +{ > > + pmd_t pmde; > > + pmd_t *pmd; > > + > > + pmd = mm_find_pmd_raw(mm, address); > > + if (!pmd) > > + goto out; > > /* > > * Some THP functions use the sequence pmdp_huge_clear_flush(), set_pmd_at() > > * without holding anon_vma lock for write. So when looking for a > > -- > > 2.36.0.rc2.479.g8af0fa9b8e-goog > > > > -- > Peter Xu >
diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h index d651f3437367..9faa678e0a5b 100644 --- a/include/trace/events/huge_memory.h +++ b/include/trace/events/huge_memory.h @@ -33,7 +33,8 @@ EM( SCAN_ALLOC_HUGE_PAGE_FAIL, "alloc_huge_page_failed") \ EM( SCAN_CGROUP_CHARGE_FAIL, "ccgroup_charge_failed") \ EM( SCAN_TRUNCATED, "truncated") \ - EMe(SCAN_PAGE_HAS_PRIVATE, "page_has_private") \ + EM( SCAN_PAGE_HAS_PRIVATE, "page_has_private") \ + EMe(SCAN_PMD_MAPPED, "page_pmd_mapped") \ #undef EM #undef EMe diff --git a/mm/internal.h b/mm/internal.h index 0667abd57634..51ae9f71a2a3 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -172,6 +172,7 @@ extern void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason /* * in mm/rmap.c: */ +pmd_t *mm_find_pmd_raw(struct mm_struct *mm, unsigned long address); extern pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address); /* diff --git a/mm/khugepaged.c b/mm/khugepaged.c index ba8dbd1825da..2933b13fc975 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -51,6 +51,7 @@ enum scan_result { SCAN_CGROUP_CHARGE_FAIL, SCAN_TRUNCATED, SCAN_PAGE_HAS_PRIVATE, + SCAN_PMD_MAPPED, }; #define CREATE_TRACE_POINTS @@ -987,6 +988,29 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address, return 0; } +static int find_pmd_or_thp_or_none(struct mm_struct *mm, + unsigned long address, + pmd_t **pmd) +{ + pmd_t pmde; + + *pmd = mm_find_pmd_raw(mm, address); + if (!*pmd) + return SCAN_PMD_NULL; + + pmde = pmd_read_atomic(*pmd); + +#ifdef CONFIG_TRANSPARENT_HUGEPAGE + /* See comments in pmd_none_or_trans_huge_or_clear_bad() */ + barrier(); +#endif + if (!pmd_present(pmde) || pmd_none(pmde)) + return SCAN_PMD_NULL; + if (pmd_trans_huge(pmde)) + return SCAN_PMD_MAPPED; + return SCAN_SUCCEED; +} + /* * Bring missing pages in from swap, to complete THP collapse. * Only done if khugepaged_scan_pmd believes it is worthwhile. @@ -1238,11 +1262,9 @@ static int khugepaged_scan_pmd(struct mm_struct *mm, VM_BUG_ON(address & ~HPAGE_PMD_MASK); - pmd = mm_find_pmd(mm, address); - if (!pmd) { - result = SCAN_PMD_NULL; + result = find_pmd_or_thp_or_none(mm, address, &pmd); + if (result != SCAN_SUCCEED) goto out; - } memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); pte = pte_offset_map_lock(mm, pmd, address, &ptl); diff --git a/mm/rmap.c b/mm/rmap.c index 61e63db5dc6f..49817f35e65c 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -759,13 +759,12 @@ unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma) return vma_address(page, vma); } -pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address) +pmd_t *mm_find_pmd_raw(struct mm_struct *mm, unsigned long address) { pgd_t *pgd; p4d_t *p4d; pud_t *pud; pmd_t *pmd = NULL; - pmd_t pmde; pgd = pgd_offset(mm, address); if (!pgd_present(*pgd)) @@ -780,6 +779,18 @@ pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address) goto out; pmd = pmd_offset(pud, address); +out: + return pmd; +} + +pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address) +{ + pmd_t pmde; + pmd_t *pmd; + + pmd = mm_find_pmd_raw(mm, address); + if (!pmd) + goto out; /* * Some THP functions use the sequence pmdp_huge_clear_flush(), set_pmd_at() * without holding anon_vma lock for write. So when looking for a
When scanning an anon pmd to see if it's eligible for collapse, return SCAN_PMD_MAPPED if the pmd already maps a THP. Note that SCAN_PMD_MAPPED is different from SCAN_PAGE_COMPOUND used in the file-collapse path, since the latter might identify pte-mapped compound pages. This is required by MADV_COLLAPSE which necessarily needs to know what hugepage-aligned/sized regions are already pmd-mapped. Signed-off-by: Zach O'Keefe <zokeefe@google.com> Reported-by: kernel test robot <lkp@intel.com> --- include/trace/events/huge_memory.h | 3 ++- mm/internal.h | 1 + mm/khugepaged.c | 30 ++++++++++++++++++++++++++---- mm/rmap.c | 15 +++++++++++++-- 4 files changed, 42 insertions(+), 7 deletions(-)