Re: [PATCH v2] migration: Count new_dirty instead of real_dirty

[zhukeqian]

Hi Dave,

On 2020/6/16 17:35, Dr. David Alan Gilbert wrote:
> * Keqian Zhu (zhukeqian1@huawei.com) wrote:
>> real_dirty_pages becomes equal to total ram size after dirty log sync
>> in ram_init_bitmaps, the reason is that the bitmap of ramblock is
>> initialized to be all set, so old path counts them as "real dirty" at
>> beginning.
>>
>> This causes wrong dirty rate and false positive throttling at the end
>> of first ram save iteration.
>>
>> Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
> 
> Since this function already returns num_dirty, why not just change the
> caller to increment a counter based off the return value?
Yes, that would be better :-) .

> 
> Can you point to the code which is using this value that triggers the
> throttle?
> 
In migration_trigger_throttle(), rs->num_dirty_pages_period is used.
And it corresponds to real_dirty_pages here.

Thanks,
Keqian

> Dave
> 
> 
[...]
>>
>>
> --
> Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
> 
> .
>