Re: [PATCH v5 03/12] migration/dirtyrate: Add RamlockDirtyInfo to store sampled page info

[Zheng Chuan]

On 2020/8/26 17:40, Zheng Chuan wrote:
> 
> 
> On 2020/8/26 17:29, David Edmondson wrote:
>> On Monday, 2020-08-24 at 17:14:31 +08, Chuan Zheng wrote:
>>
>>> Add RamlockDirtyInfo to store sampled page info of each ramblock.
>>>
>>> Signed-off-by: Chuan Zheng <zhengchuan@huawei.com>
>>> ---
>>>  migration/dirtyrate.h | 18 ++++++++++++++++++
>>>  1 file changed, 18 insertions(+)
>>>
>>> diff --git a/migration/dirtyrate.h b/migration/dirtyrate.h
>>> index 33669b7..70000da 100644
>>> --- a/migration/dirtyrate.h
>>> +++ b/migration/dirtyrate.h
>>> @@ -19,6 +19,11 @@
>>>   */
>>>  #define DIRTYRATE_DEFAULT_SAMPLE_PAGES            512
>>>  
>>> +/*
>>> + * Record ramblock idstr
>>> + */
>>> +#define RAMBLOCK_INFO_MAX_LEN                     256
>>> +
>>>  /* Take 1s as default for calculation duration */
>>>  #define DEFAULT_FETCH_DIRTYRATE_TIME_SEC          1
>>>  
>>> @@ -27,6 +32,19 @@ struct DirtyRateConfig {
>>>      int64_t sample_period_seconds; /* time duration between two sampling */
>>>  };
>>>  
>>> +/*
>>> + * Store dirtypage info for each ramblock.
>>> + */
>>> +struct RamblockDirtyInfo {
>>> +    char idstr[RAMBLOCK_INFO_MAX_LEN]; /* idstr for each ramblock */
>>> +    uint8_t *ramblock_addr; /* base address of ramblock we measure */
>>> +    uint64_t ramblock_pages; /* ramblock size in 4K-page */
>>
>> It's probably a stupid question, but why not store a pointer to the
>> RAMBlock rather than copying some of the details?
>>
Missing this question:)
Since I only hold the RCU around each part separately, the RAMBlock
could disappear between the initial hash, and the later compare;  so
using the name makes it safe.
Again, Please refer to the newer patch series:)

>>> +    uint64_t *sample_page_vfn; /* relative offset address for sampled page 
>>> */
>>> +    uint64_t sample_pages_count; /* count of sampled pages */
>>> +    uint64_t sample_dirty_count; /* cout of dirty pages we measure */
>>
>> "cout" -> "count"
>>
> Hi, David.
> Thank you for review.
> Actually I have resent [PATCH V5], but it's my fault to forget to add resent 
> tag which may lead to confusing.
> In new patch series, this spell mistake is fixed.
> Please refer to the newer patch series:)
> 
>>> +    uint32_t *hash_result; /* array of hash result for sampled pages */
>>> +};
>>> +
>>>  void *get_dirtyrate_thread(void *arg);
>>>  #endif
>>>  
>>> -- 
>>> 1.8.3.1
>>
>> dme.
>>