> On Jul 30, 2019, at 8:01 AM, Kirill A. Shutemov <[email protected]> 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 <[email protected]>
>> ---
>> 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
