Re: [PATCH v3 06/10] migration/dirtyrate: Compare page hash results for recorded sampled page

[Zheng Chuan]

On 2020/8/21 1:36, Dr. David Alan Gilbert wrote:
> * Chuan Zheng (zhengchuan@huawei.com) wrote:
>> Compare page hash results for recorded sampled page.
>>
>> Signed-off-by: Chuan Zheng <zhengchuan@huawei.com>
>> Signed-off-by: YanYing Zhuang <ann.zhuangyanying@huawei.com>
>> ---
>>  migration/dirtyrate.c | 76 
>> +++++++++++++++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 76 insertions(+)
>>
>> diff --git a/migration/dirtyrate.c b/migration/dirtyrate.c
>> index 62b6f69..3ce25f5 100644
>> --- a/migration/dirtyrate.c
>> +++ b/migration/dirtyrate.c
>> @@ -215,6 +215,82 @@ static int record_ramblock_hash_info(struct 
>> RamblockDirtyInfo **block_dinfo,
>>      return 0;
>>  }
>>  
>> +static int calc_page_dirty_rate(struct RamblockDirtyInfo *info)
>> +{
>> +    uint8_t *md = NULL;
>> +    int i;
>> +    int ret = 0;
>> +
>> +    md = g_try_new0(uint8_t, qcrypto_hash_len);
>> +    if (!md) {
>> +        return -1;
>> +    }
> 
> As previously asked; isn't this a nice small simple fixed length - no
> need to allocate it?
> 
Yes, it could use QCRYPTO_HASH_LEN to define an array.
>> +
>> +    for (i = 0; i < info->sample_pages_count; i++) {
>> +        ret = get_ramblock_vfn_hash(info, info->sample_page_vfn[i], &md);
>> +        if (ret < 0) {
>> +            goto out;
>> +        }
>> +
>> +        if (memcmp(md, info->hash_result + i * qcrypto_hash_len,
>> +                   qcrypto_hash_len) != 0) {
>> +            info->sample_dirty_count++;
>> +        }
>> +    }
>> +
>> +out:
>> +    g_free(md);
>> +    return ret;
>> +}
>> +
>> +static bool find_page_matched(RAMBlock *block, struct RamblockDirtyInfo 
>> *infos,
>> +                              int count, struct RamblockDirtyInfo **matched)
>> +{
>> +    int i;
>> +
>> +    for (i = 0; i < count; i++) {
>> +        if (!strcmp(infos[i].idstr, qemu_ram_get_idstr(block))) {
>> +            break;
>> +        }
>> +    }
>> +
>> +    if (i == count) {
>> +        return false;
>> +    }
>> +
>> +    if (infos[i].ramblock_addr != qemu_ram_get_host_addr(block) ||
>> +        infos[i].ramblock_pages !=
>> +            (qemu_ram_get_used_length(block) >> 12)) {
>> +        return false;
> 
> I previously asked how this happens.
> Also this was DIRTYRATE_PAGE_SIZE_SHIFT
> 
Here, we want to find same ramblock we sampled before.
We just ignore the ramblock if its hva address or size changed due to memory 
hot-plug during the measurement.

>> +    }
>> +
>> +    *matched = &infos[i];
>> +    return true;
>> +}
>> +
>> +static int compare_page_hash_info(struct RamblockDirtyInfo *info,
>> +                                  int block_index)
>> +{
>> +    struct RamblockDirtyInfo *block_dinfo = NULL;
>> +    RAMBlock *block = NULL;
>> +
>> +    RAMBLOCK_FOREACH_MIGRATABLE(block) {
>> +        block_dinfo = NULL;
> 
> So you've removed the selction of only some RAMBlocks now?
> 
In next patch:), i add functions to skip sampling ramblock.

>> +        if (!find_page_matched(block, info, block_index + 1, &block_dinfo)) 
>> {
>> +            continue;
>> +        }
>> +        if (calc_page_dirty_rate(block_dinfo) < 0) {
>> +            return -1;
>> +        }
>> +        update_dirtyrate_stat(block_dinfo);
>> +    }
>> +    if (!dirty_stat.total_sample_count) {
>> +        return -1;
>> +    }
>> +
>> +    return 0;
>> +}
>> +
>>  static void calculate_dirtyrate(struct DirtyRateConfig config)
>>  {
>>      /* todo */
>> -- 
>> 1.8.3.1
>>