[CRIU] [PATCH 3/3] criu: lazy-pages: use new pagemap features

[Pavel Emelyanov]

On 06/28/2016 04:42 PM, Mike Rapoport wrote:
> On Tue, Jun 28, 2016 at 4:07 PM, Pavel Emelyanov <xemul at virtuozzo.com> wrote:
>> On 06/27/2016 07:53 AM, Mike Rapoport wrote:
>>> Pagemap now is more friendly to random accesses, enable use of new APIs.
>>>
>>> Signed-off-by: Mike Rapoport <rppt at linux.vnet.ibm.com>
>>> ---
>>>  criu/uffd.c | 29 +++++++++--------------------
>>>  1 file changed, 9 insertions(+), 20 deletions(-)
>>>
>>> diff --git a/criu/uffd.c b/criu/uffd.c
>>> index a920ae7..1e0a57a 100644
>>> --- a/criu/uffd.c
>>> +++ b/criu/uffd.c
>>> @@ -46,6 +46,8 @@ struct lazy_pages_info {
>>>
>>>       struct list_head pages;
>>>
>>> +     struct page_read pr;
>>> +
>>>       unsigned long total_pages;
>>>       unsigned long copied_pages;
>>>
>>> @@ -76,6 +78,8 @@ static void lpi_fini(struct lazy_pages_info *lpi)
>>>  {
>>>       if (lpi->uffd)
>>>               close(lpi->uffd);
>>> +     if (lpi->pr.close)
>>> +             lpi->pr.close(&lpi->pr);
>>>       free(lpi);
>>>  }
>>>
>>> @@ -326,34 +330,23 @@ out:
>>>
>>>  static int get_page(struct lazy_pages_info *lpi, unsigned long addr, void *dest)
>>>  {
>>> -     struct iovec iov;
>>>       int ret;
>>>       unsigned char buf[PAGE_SIZE];
>>> -     struct page_read pr;
>>> -
>>> -     ret = open_page_read(lpi->pid, &pr, PR_TASK | PR_MOD);
>>> -     pr_debug("get_page ret %d\n", ret);
>>>
>>> -     ret = pr.get_pagemap(&pr, &iov);
>>> -     pr_debug("get_pagemap ret %d\n", ret);
>>> -     if (ret <= 0)
>>> -             return ret;
>>> +     lpi->pr.reset(&lpi->pr);
>>
>> Maybe it's better to reset the pr _only_ if the requesting address is below the
>> recently read one?
> 
> Like
>         get_pagemap(&pr, &iov);
>         if (addr < iov.iov_base)
>                 pr.reset()
> ?
> 
> It should be slightly faster, yeah.
> Wanna patch? ;-)

I definitely do :)

>>>
>>> -     ret = pr.seek_page(&pr, addr, true);
>>> +     ret = lpi->pr.seek_page(&lpi->pr, addr, true);
>>>       pr_debug("seek_pagemap_page ret 0x%x\n", ret);
>>>       if (ret <= 0)
>>>               return ret;
>>>
>>> -     ret = pr.read_pages(&pr, addr, 1, buf);
>>> +     ret = lpi->pr.read_pages(&lpi->pr, addr, 1, buf);
>>>       pr_debug("read_pages ret %d\n", ret);
>>>       if (ret <= 0)
>>>               return ret;
>>>
>>>       memcpy(dest, buf, PAGE_SIZE);
>>>
>>> -     if (pr.close)
>>> -             pr.close(&pr);
>>> -
>>>       return 1;
>>>  }
>>>
>>> @@ -560,7 +553,6 @@ static int find_vmas(struct lazy_pages_info *lpi)
>>>       struct vm_area_list vmas;
>>>       int vn = 0;
>>>       struct rst_info *ri;
>>> -     struct page_read pr;
>>>       struct uffd_pages_struct *uffd_pages;
>>>       struct pstree_item *item = pstree_item_by_virt(lpi->pid);
>>>
>>> @@ -606,7 +598,7 @@ static int find_vmas(struct lazy_pages_info *lpi)
>>>               pr_info("vma 0x%"PRIx64" 0x%"PRIx64"\n", vma->e->start, vma->e->end);
>>>       }
>>>
>>> -     ret = open_page_read(lpi->pid, &pr, PR_TASK);
>>> +     ret = open_page_read(lpi->pid, &lpi->pr, PR_TASK);
>>>       if (ret <= 0) {
>>>               ret = -1;
>>>               goto out;
>>> @@ -618,15 +610,12 @@ static int find_vmas(struct lazy_pages_info *lpi)
>>>        * pushed into the process using userfaultfd.
>>>        */
>>>       do {
>>> -             ret = collect_uffd_pages(&pr, lpi);
>>> +             ret = collect_uffd_pages(&lpi->pr, lpi);
>>>               if (ret == -1) {
>>>                       goto out;
>>>               }
>>>       } while (ret);
>>>
>>> -     if (pr.close)
>>> -             pr.close(&pr);
>>> -
>>>       /* Count detected pages */
>>>       list_for_each_entry(uffd_pages, &lpi->pages, list)
>>>           ret++;
>>>
>>
> 
> 
>