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Re: [PATCH v2] migration: Count new_dirty instead of real_dirty
From: |
zhukeqian |
Subject: |
Re: [PATCH v2] migration: Count new_dirty instead of real_dirty |
Date: |
Tue, 16 Jun 2020 17:48:57 +0800 |
User-agent: |
Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.7.1 |
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
>
> .
>