Re: [Qemu-devel] [PATCH 16/51] ram: Move iterations into RAMState

[Juan Quintela]

Peter Xu <address@hidden> wrote:
> On Thu, Mar 23, 2017 at 09:45:09PM +0100, Juan Quintela wrote:
>> Signed-off-by: Juan Quintela <address@hidden>

>> @@ -693,13 +694,13 @@ static void migration_bitmap_sync(RAMState *rs)
>>          }
>>  
>>          if (migrate_use_xbzrle()) {
>> -            if (rs->iterations_prev != acct_info.iterations) {
>> +            if (rs->iterations_prev != rs->iterations) {
>>                  acct_info.xbzrle_cache_miss_rate =
>>                     (double)(acct_info.xbzrle_cache_miss -
>>                              rs->xbzrle_cache_miss_prev) /
>> -                   (acct_info.iterations - rs->iterations_prev);
>> +                   (rs->iterations - rs->iterations_prev);
>
> Here we are calculating cache miss rate by xbzrle_cache_miss and
> iterations. However looks like xbzrle_cache_miss is counted per guest
> page (in save_xbzrle_page()) while the iteration count is per host
> page (in ram_save_iterate()). Then, what if host page size not equals
> to guest page size? E.g., when host uses 2M huge pages, host page size
> is 2M, while guest page size can be 4K?

Good catch.  Will have to think about this.  You are right.  I will
change that later.

Thanks, Juan.