Re: [Qemu-devel] [PATCH 2/4] migration: set dirty_pages_rate before autoconverge logic

[Felipe Franciosi]

> On 25 May 2017, at 01:40, Peter Xu <address@hidden> wrote:
> 
> On Wed, May 24, 2017 at 05:10:01PM +0100, Felipe Franciosi wrote:
>> Currently, a "period" in the RAM migration logic is at least a second
>> long and accounts for what happened since the last period (or the
>> beginning of the migration). The dirty_pages_rate counter is calculated
>> at the end this logic.
>> 
>> If the auto convergence capability is enabled from the start of the
>> migration, it won't be able to use this counter the first time around.
>> This calculates dirty_pages_rate as soon as a period is deemed over,
>> which allows for it to be used immediately.
>> 
>> Signed-off-by: Felipe Franciosi <address@hidden>
> 
> You fixed the indents as well, but imho it's okay.

Yeah a couple of lines were off-by-one space. Fixed it given I was touching the 
code anyway, hope it's ok with everyone else. Would you normally patch that 
separately or just mention it in the commit message?

F.

> 
> Reviewed-by: Peter Xu <address@hidden>
> 
>> ---
>> migration/ram.c | 17 ++++++++++-------
>> 1 file changed, 10 insertions(+), 7 deletions(-)
>> 
>> diff --git a/migration/ram.c b/migration/ram.c
>> index 36bf720..495ecbe 100644
>> --- a/migration/ram.c
>> +++ b/migration/ram.c
>> @@ -694,6 +694,10 @@ static void migration_bitmap_sync(RAMState *rs)
>> 
>>     /* more than 1 second = 1000 millisecons */
>>     if (end_time > rs->time_last_bitmap_sync + 1000) {
>> +        /* calculate period counters */
>> +        rs->dirty_pages_rate = rs->num_dirty_pages_period * 1000
>> +            / (end_time - rs->time_last_bitmap_sync);
>> +
>>         if (migrate_auto_converge()) {
>>             /* The following detection logic can be refined later. For now:
>>                Check to see if the dirtied bytes is 50% more than the approx.
>> @@ -702,15 +706,14 @@ static void migration_bitmap_sync(RAMState *rs)
>>                throttling */
>>             bytes_xfer_now = ram_bytes_transferred();
>> 
>> -            if (rs->dirty_pages_rate &&
>> -               (rs->num_dirty_pages_period * TARGET_PAGE_SIZE >
>> +            if ((rs->num_dirty_pages_period * TARGET_PAGE_SIZE >
>>                    (bytes_xfer_now - rs->bytes_xfer_prev) / 2) &&
>> -               (rs->dirty_rate_high_cnt++ >= 2)) {
>> +                (rs->dirty_rate_high_cnt++ >= 2)) {
>>                     trace_migration_throttle();
>>                     rs->dirty_rate_high_cnt = 0;
>>                     mig_throttle_guest_down();
>> -             }
>> -             rs->bytes_xfer_prev = bytes_xfer_now;
>> +            }
>> +            rs->bytes_xfer_prev = bytes_xfer_now;
>>         }
>> 
>>         if (migrate_use_xbzrle()) {
>> @@ -723,8 +726,8 @@ static void migration_bitmap_sync(RAMState *rs)
>>             rs->iterations_prev = rs->iterations;
>>             rs->xbzrle_cache_miss_prev = rs->xbzrle_cache_miss;
>>         }
>> -        rs->dirty_pages_rate = rs->num_dirty_pages_period * 1000
>> -            / (end_time - rs->time_last_bitmap_sync);
>> +
>> +        /* reset period counters */
>>         rs->time_last_bitmap_sync = end_time;
>>         rs->num_dirty_pages_period = 0;
>>     }
>> -- 
>> 1.9.5
>> 
> 
> -- 
> Peter Xu