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Re: [PATCH v6 10/12] migration/dirtyrate: Implement calculate_dirtyrate(


From: Zheng Chuan
Subject: Re: [PATCH v6 10/12] migration/dirtyrate: Implement calculate_dirtyrate() function
Date: Mon, 31 Aug 2020 19:24:04 +0800
User-agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0


On 2020/8/31 17:13, David Edmondson wrote:
> On Saturday, 2020-08-29 at 10:52:55 +08, Chuan Zheng wrote:
> 
>> Implement calculate_dirtyrate() function.
>>
>> Signed-off-by: Chuan Zheng <zhengchuan@huawei.com>
>> Signed-off-by: YanYing Zhuang <ann.zhuangyanying@huawei.com>
>> ---
>>  migration/dirtyrate.c | 45 +++++++++++++++++++++++++++++++++++++++++++--
>>  1 file changed, 43 insertions(+), 2 deletions(-)
>>
>> diff --git a/migration/dirtyrate.c b/migration/dirtyrate.c
>> index 850126d..95ee23e 100644
>> --- a/migration/dirtyrate.c
>> +++ b/migration/dirtyrate.c
>> @@ -162,6 +162,21 @@ static void get_ramblock_dirty_info(RAMBlock *block,
>>      strcpy(info->idstr, qemu_ram_get_idstr(block));
>>  }
>>  
>> +static void free_ramblock_dirty_info(struct RamblockDirtyInfo *infos, int 
>> count)
>> +{
>> +    int i;
>> +
>> +    if (!infos) {
>> +        return;
>> +    }
>> +
>> +    for (i = 0; i < count; i++) {
>> +        g_free(infos[i].sample_page_vfn);
>> +        g_free(infos[i].hash_result);
>> +    }
>> +    g_free(infos);
>> +}
>> +
>>  static struct RamblockDirtyInfo *
>>  alloc_ramblock_dirty_info(int *block_index,
>>                            struct RamblockDirtyInfo *block_dinfo)
>> @@ -301,8 +316,34 @@ static int compare_page_hash_info(struct 
>> RamblockDirtyInfo *info,
>>  
>>  static void calculate_dirtyrate(struct DirtyRateConfig config)
>>  {
>> -    /* todo */
>> -    return;
>> +    struct RamblockDirtyInfo *block_dinfo = NULL;
>> +    int block_index = 0;
>> +    int64_t msec = 0;
>> +    int64_t initial_time;
>> +
>> +    rcu_register_thread();
>> +    reset_dirtyrate_stat();
>> +    rcu_read_lock();
>> +    initial_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
>> +    if (record_ramblock_hash_info(&block_dinfo, config, &block_index) < 0) {
>> +        goto out;
>> +    }
>> +    rcu_read_unlock();
>> +
>> +    msec = config.sample_period_seconds * 1000;
>> +    msec = set_sample_page_period(msec, initial_time);
>> +
>> +    rcu_read_lock();
>> +    if (compare_page_hash_info(block_dinfo, block_index) < 0) {
>> +        goto out;
>> +    }
>> +
>> +    update_dirtyrate(msec);
>> +
>> +out:
>> +    rcu_read_unlock();
> 
> This still holds the RCU lock across update_dirtyrate(), which I
> understood to be unnecessary.
>It does need to update_dirtyrate if we goto out when erro happens.
In order to remove update_dirtyrate out of RCU, it need to add flag
like is_need_update, like:
if (record_ramblock_hash_info(&block_dinfo, config, &block_index) < 0) {
         is_need_update = false;
         goto out;
}

if (is_need_update)
    update_dirtyrate(msec);

I doubt it is worth doing that or it will does any hurt if i holds
the RCU lock across update_dirtyrate()?


>> +    free_ramblock_dirty_info(block_dinfo, block_index + 1);
>> +    rcu_unregister_thread();
>>  }
>>  
>>  void *get_dirtyrate_thread(void *arg)
>> -- 
>> 1.8.3.1
> 
> dme.
> 




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