On Wednesday, 2021-03-03 at 19:47:20 +08, Kunkun Jiang wrote:
> On 2021/3/3 16:56, David Edmondson wrote:
>> On Monday, 2021-03-01 at 16:21:32 +08, Kunkun Jiang wrote:
>>
>>> Starting from pss->page, ram_save_host_page() will check every page
>>> and send the dirty pages up to the end of the current host page or
>>> the boundary of used_length of the block. If the host page size is
>>> a huge page, the step "check" will take a lot of time.
>>>
>>> This will improve performance to use migration_bitmap_find_dirty().
>> This is cleaner, thank you.
>>
>> I was hoping to just invert the body of the loop - something like
>> (completely untested):
> Sorry for my misunderstanding.
No, I explained myself poorly.
> I will improve it in the next version.
>> do {
>> int pages_this_iteration = 0;
>>
>> /* Check if the page is dirty and, if so, send it. */
>> if (migration_bitmap_clear_dirty(rs, pss->block, pss->page)) {
>> pages_this_iteration = ram_save_target_page(rs, pss, last_stage);
>> if (pages_this_iteration < 0) {
>> return pages_this_iteration;
>> }
>>
>> pages += pages_this_iteration;
>>
>> /*
>> * Allow rate limiting to happen in the middle of huge pages if
>> * the current iteration sent something.
>> */
>> if (pagesize_bits > 1 && pages_this_iteration > 0) {
>> migration_rate_limit();
>> }
> I missed the case that the value of pages_this_iteration is 0. 😅
I don't think that your version was wrong, because it returned early
from the loop if there were no candidate pages.
>> }
>> pss->page = migration_bitmap_find_dirty(rs, pss->block, pss->page);
>> } while ((pss->page < hostpage_boundary) &&
>> offset_in_ramblock(pss->block,
>> ((ram_addr_t)pss->page) << TARGET_PAGE_BITS));
>> /* The offset we leave with is the min boundary of host page and block */
>> pss->page = MIN(pss->page, hostpage_boundary) - 1;
>
> Best Regards.
>
> Kunkun Jiang
>
>>> Signed-off-by: Keqian Zhu <zhukeqi...@huawei.com>
>>> Signed-off-by: Kunkun Jiang <jiangkun...@huawei.com>
>>> ---
>>> migration/ram.c | 12 +++++++-----
>>> 1 file changed, 7 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/migration/ram.c b/migration/ram.c
>>> index 3a9115b6dc..a1374db356 100644
>>> --- a/migration/ram.c
>>> +++ b/migration/ram.c
>>> @@ -1991,6 +1991,8 @@ static int ram_save_host_page(RAMState *rs,
>>> PageSearchStatus *pss,
>>> int tmppages, pages = 0;
>>> size_t pagesize_bits =
>>> qemu_ram_pagesize(pss->block) >> TARGET_PAGE_BITS;
>>> + unsigned long hostpage_boundary =
>>> + QEMU_ALIGN_UP(pss->page + 1, pagesize_bits);
>>> unsigned long start_page = pss->page;
>>> int res;
>>>
>>> @@ -2002,7 +2004,7 @@ static int ram_save_host_page(RAMState *rs,
>>> PageSearchStatus *pss,
>>> do {
>>> /* Check the pages is dirty and if it is send it */
>>> if (!migration_bitmap_clear_dirty(rs, pss->block, pss->page)) {
>>> - pss->page++;
>>> + pss->page = migration_bitmap_find_dirty(rs, pss->block,
>>> pss->page);
>>> continue;
>>> }
>>>
>>> @@ -2012,16 +2014,16 @@ static int ram_save_host_page(RAMState *rs,
>>> PageSearchStatus *pss,
>>> }
>>>
>>> pages += tmppages;
>>> - pss->page++;
>>> + pss->page = migration_bitmap_find_dirty(rs, pss->block, pss->page);
>>> /* Allow rate limiting to happen in the middle of huge pages */
>>> if (pagesize_bits > 1) {
>>> migration_rate_limit();
>>> }
>>> - } while ((pss->page & (pagesize_bits - 1)) &&
>>> + } while ((pss->page < hostpage_boundary) &&
>>> offset_in_ramblock(pss->block,
>>> ((ram_addr_t)pss->page) <<
>>> TARGET_PAGE_BITS));
>>> - /* The offset we leave with is the last one we looked at */
>>> - pss->page--;
>>> + /* The offset we leave with is the min boundary of host page and block
>>> */
>>> + pss->page = MIN(pss->page, hostpage_boundary) - 1;
>>>
>>> res = ram_save_release_protection(rs, pss, start_page);
>>> return (res < 0 ? res : pages);
>>> --
>>> 2.23.0
>> dme.
dme.
--
Too much information, running through my brain.
