| Message ID | 20190729054335.3241150-3-songliubraving@fb.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | khugepaged: collapse pmd for pte-mapped THP | expand |
On Sun, Jul 28, 2019 at 10:43:35PM -0700, Song Liu wrote: > After all uprobes are removed from the huge page (with PTE pgtable), it > is possible to collapse the pmd and benefit from THP again. This patch > does the collapse by calling khugepaged_add_pte_mapped_thp(). > > Signed-off-by: Song Liu <songliubraving@fb.com> > --- > kernel/events/uprobes.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c > index 58ab7fc7272a..cc53789fefc6 100644 > --- a/kernel/events/uprobes.c > +++ b/kernel/events/uprobes.c > @@ -26,6 +26,7 @@ > #include <linux/percpu-rwsem.h> > #include <linux/task_work.h> > #include <linux/shmem_fs.h> > +#include <linux/khugepaged.h> > > #include <linux/uprobes.h> > > @@ -470,6 +471,7 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm, > struct page *old_page, *new_page; > struct vm_area_struct *vma; > int ret, is_register, ref_ctr_updated = 0; > + bool orig_page_huge = false; > > is_register = is_swbp_insn(&opcode); > uprobe = container_of(auprobe, struct uprobe, arch); > @@ -525,6 +527,9 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm, > > /* dec_mm_counter for old_page */ > dec_mm_counter(mm, MM_ANONPAGES); > + > + if (PageCompound(orig_page)) > + orig_page_huge = true; > } > put_page(orig_page); > } > @@ -543,6 +548,10 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm, > if (ret && is_register && ref_ctr_updated) > update_ref_ctr(uprobe, mm, -1); > > + /* try collapse pmd for compound page */ > + if (!ret && orig_page_huge) > + khugepaged_add_pte_mapped_thp(mm, vaddr & HPAGE_PMD_MASK); > + IIUC, here you have all locks taken, so you should be able to call collapse_pte_mapped_thp() directly, shouldn't you?
> On Jul 30, 2019, at 8:01 AM, Kirill A. Shutemov <kirill@shutemov.name> wrote: > > On Sun, Jul 28, 2019 at 10:43:35PM -0700, Song Liu wrote: >> After all uprobes are removed from the huge page (with PTE pgtable), it >> is possible to collapse the pmd and benefit from THP again. This patch >> does the collapse by calling khugepaged_add_pte_mapped_thp(). >> >> Signed-off-by: Song Liu <songliubraving@fb.com> >> --- >> kernel/events/uprobes.c | 9 +++++++++ >> 1 file changed, 9 insertions(+) >> >> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c >> index 58ab7fc7272a..cc53789fefc6 100644 >> --- a/kernel/events/uprobes.c >> +++ b/kernel/events/uprobes.c >> @@ -26,6 +26,7 @@ >> #include <linux/percpu-rwsem.h> >> #include <linux/task_work.h> >> #include <linux/shmem_fs.h> >> +#include <linux/khugepaged.h> >> >> #include <linux/uprobes.h> >> >> @@ -470,6 +471,7 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm, >> struct page *old_page, *new_page; >> struct vm_area_struct *vma; >> int ret, is_register, ref_ctr_updated = 0; >> + bool orig_page_huge = false; >> >> is_register = is_swbp_insn(&opcode); >> uprobe = container_of(auprobe, struct uprobe, arch); >> @@ -525,6 +527,9 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm, >> >> /* dec_mm_counter for old_page */ >> dec_mm_counter(mm, MM_ANONPAGES); >> + >> + if (PageCompound(orig_page)) >> + orig_page_huge = true; >> } >> put_page(orig_page); >> } >> @@ -543,6 +548,10 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm, >> if (ret && is_register && ref_ctr_updated) >> update_ref_ctr(uprobe, mm, -1); >> >> + /* try collapse pmd for compound page */ >> + if (!ret && orig_page_huge) >> + khugepaged_add_pte_mapped_thp(mm, vaddr & HPAGE_PMD_MASK); >> + > > IIUC, here you have all locks taken, so you should be able to call > collapse_pte_mapped_thp() directly, shouldn't you? > Yes, we can call it directly. I had it that way in a very early version. Let me do that in the next version. Thanks, Song
On 07/28, Song Liu wrote: > > @@ -525,6 +527,9 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm, > > /* dec_mm_counter for old_page */ > dec_mm_counter(mm, MM_ANONPAGES); > + > + if (PageCompound(orig_page)) > + orig_page_huge = true; I am wondering how find_get_page() can return a PageCompound() page... IIUC, this is only possible if shmem_file(), right? Oleg.
> On Jul 31, 2019, at 9:16 AM, Oleg Nesterov <oleg@redhat.com> wrote: > > On 07/28, Song Liu wrote: >> >> @@ -525,6 +527,9 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm, >> >> /* dec_mm_counter for old_page */ >> dec_mm_counter(mm, MM_ANONPAGES); >> + >> + if (PageCompound(orig_page)) >> + orig_page_huge = true; > > I am wondering how find_get_page() can return a PageCompound() page... > > IIUC, this is only possible if shmem_file(), right? Yes, this is the case at the moment. We will be able to do it for other file systems when this set gets in: https://lkml.org/lkml/2019/6/24/1531 Thanks, Song
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 58ab7fc7272a..cc53789fefc6 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -26,6 +26,7 @@ #include <linux/percpu-rwsem.h> #include <linux/task_work.h> #include <linux/shmem_fs.h> +#include <linux/khugepaged.h> #include <linux/uprobes.h> @@ -470,6 +471,7 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm, struct page *old_page, *new_page; struct vm_area_struct *vma; int ret, is_register, ref_ctr_updated = 0; + bool orig_page_huge = false; is_register = is_swbp_insn(&opcode); uprobe = container_of(auprobe, struct uprobe, arch); @@ -525,6 +527,9 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm, /* dec_mm_counter for old_page */ dec_mm_counter(mm, MM_ANONPAGES); + + if (PageCompound(orig_page)) + orig_page_huge = true; } put_page(orig_page); } @@ -543,6 +548,10 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm, if (ret && is_register && ref_ctr_updated) update_ref_ctr(uprobe, mm, -1); + /* try collapse pmd for compound page */ + if (!ret && orig_page_huge) + khugepaged_add_pte_mapped_thp(mm, vaddr & HPAGE_PMD_MASK); + return ret; }
After all uprobes are removed from the huge page (with PTE pgtable), it is possible to collapse the pmd and benefit from THP again. This patch does the collapse by calling khugepaged_add_pte_mapped_thp(). Signed-off-by: Song Liu <songliubraving@fb.com> --- kernel/events/uprobes.c | 9 +++++++++ 1 file changed, 9 insertions(+)