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

[Mike Rapoport]

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? ;-)

>>
>> -     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++;
>>
>



-- 
Sincerely yours,
Mike.