Re: [Qemu-devel] [PATCH] Change the method to calculate dirty-pages-rate

[Chao Fan]

On Tue, Mar 14, 2017 at 09:41:30AM +0800, Li Zhijian wrote:
>
>
>On 03/14/2017 09:26 AM, Chao Fan wrote:
>> In function cpu_physical_memory_sync_dirty_bitmap, file
>> include/exec/ram_addr.h:
>> 
>> if (src[idx][offset]) {
>>     unsigned long bits = atomic_xchg(&src[idx][offset], 0);
>>     unsigned long new_dirty;
>>     new_dirty = ~dest[k];
>>     dest[k] |= bits;
>>     new_dirty &= bits;
>>     num_dirty += ctpopl(new_dirty);
>> }
>> 
>> After these codes executed, only the pages not dirtied in bitmap(dest),
>> but dirtied in dirty_memory[DIRTY_MEMORY_MIGRATION] will be calculated.
>> For example:
>> When ram_list.dirty_memory[DIRTY_MEMORY_MIGRATION] = 0b00001111,
>> and atomic_rcu_read(&migration_bitmap_rcu)->bmap = 0b00000011,
>> the new_dirty will be 0b00001100, and this function will return 2 but not
>> 4 which is expected.
>> the dirty pages in dirty_memory[DIRTY_MEMORY_MIGRATION] are all new,
>> so these should be calculated also.
>> 
>> Signed-off-by: Chao Fan <address@hidden>
>> Signed-off-by: Li Zhijian <address@hidden>
>> ---
>>  include/exec/ram_addr.h | 5 ++++-
>>  migration/ram.c         | 7 +++----
>>  2 files changed, 7 insertions(+), 5 deletions(-)
>> 
>> diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
>> index cd432e7..b05dc84 100644
>> --- a/include/exec/ram_addr.h
>> +++ b/include/exec/ram_addr.h
>> @@ -355,7 +355,8 @@ static inline void 
>> cpu_physical_memory_clear_dirty_range(ram_addr_t start,
>>  static inline
>>  uint64_t cpu_physical_memory_sync_dirty_bitmap(unsigned long *dest,
>>                                                 ram_addr_t start,
>> -                                               ram_addr_t length)
>> +                                               ram_addr_t length,
>> +                                               int64_t *real_dirty_pages)
>>  {
>>      ram_addr_t addr;
>>      unsigned long page = BIT_WORD(start >> TARGET_PAGE_BITS);
>> @@ -379,6 +380,7 @@ uint64_t cpu_physical_memory_sync_dirty_bitmap(unsigned 
>> long *dest,
>>              if (src[idx][offset]) {
>>                  unsigned long bits = atomic_xchg(&src[idx][offset], 0);
>>                  unsigned long new_dirty;
>> +                *real_dirty_pages += ctpopl(bits);
>>                  new_dirty = ~dest[k];
>>                  dest[k] |= bits;
>>                  new_dirty &= bits;
>> @@ -398,6 +400,7 @@ uint64_t cpu_physical_memory_sync_dirty_bitmap(unsigned 
>> long *dest,
>>                          start + addr,
>>                          TARGET_PAGE_SIZE,
>>                          DIRTY_MEMORY_MIGRATION)) {
>> +                *real_dirty_pages += 1;
>>                  long k = (start + addr) >> TARGET_PAGE_BITS;
>>                  if (!test_and_set_bit(k, dest)) {
>>                      num_dirty++;
>> diff --git a/migration/ram.c b/migration/ram.c
>> index 719425b..fdf9a85 100644
>> --- a/migration/ram.c
>> +++ b/migration/ram.c
>> @@ -576,18 +576,18 @@ static inline bool 
>> migration_bitmap_clear_dirty(ram_addr_t addr)
>>      return ret;
>>  }
>> 
>> +static int64_t num_dirty_pages_period;
>>  static void migration_bitmap_sync_range(ram_addr_t start, ram_addr_t length)
>>  {
>>      unsigned long *bitmap;
>>      bitmap = atomic_rcu_read(&migration_bitmap_rcu)->bmap;
>> -    migration_dirty_pages +=
>> -        cpu_physical_memory_sync_dirty_bitmap(bitmap, start, length);
>> +    migration_dirty_pages += cpu_physical_memory_sync_dirty_bitmap(bitmap,
>> +                             start, length, &num_dirty_pages_period);
>>  }
>> 
>>  /* Fix me: there are too many global variables used in migration process. */
>>  static int64_t start_time;
>>  static int64_t bytes_xfer_prev;
>> -static int64_t num_dirty_pages_period;
>>  static uint64_t xbzrle_cache_miss_prev;
>>  static uint64_t iterations_prev;
>> 
>> @@ -648,7 +648,6 @@ static void migration_bitmap_sync(void)
>> 
>>      trace_migration_bitmap_sync_end(migration_dirty_pages
>>                                      - num_dirty_pages_init);
>> -    num_dirty_pages_period += migration_dirty_pages - num_dirty_pages_init;
>
>it seems num_dirty_pages_init should be removed also and update 
>trace_migration_bitmap_sync_end()'s parameter.
Hi Li Zhijian,

OK, I will update and resend the V2 version.

Thanks,
Chao Fan
>
>
>Thanks
>Zhijian
>
>>      end_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
>> 
>>      /* more than 1 second = 1000 millisecons */
>> 
>