Re: [Qemu-devel] [PATCH 1/2] migration: bitmap_set is unnecessary as bitmap_new uses g_try_malloc0

["Denis V. Lunev" <den@openvz.org>]

On 09/25/2015 12:24 PM, Wen Congyang wrote:
> On 09/25/2015 05:09 PM, Denis V. Lunev wrote:
>> we can omit calling of bitmap_set in migration_bitmap_extend and
>> ram_save_setup just after bitmap_new, which properly zeroes memory
>> inside.
> This patch is wrong. bitmap_set() is set all bits of the memory to 1,
> not 0.
>

OK, then I'll replace g_try_malloc0 with g_try_malloc in the next patch 
to avoid
double memset

>> Signed-off-by: Denis V. Lunev <den@openvz.org>
>> CC: Igor Redko <redkoi@virtuozzo.com>
>> CC: Anna Melekhova <annam@virtuozzo.com>
>> CC: Juan Quintela <quintela@redhat.com>
>> CC: Amit Shah <amit.shah@redhat.com>
>> CC: Wen Congyang <wency@cn.fujitsu.com>
>> ---
>>   migration/ram.c | 2 --
>>   1 file changed, 2 deletions(-)
>>
>> diff --git a/migration/ram.c b/migration/ram.c
>> index 7f007e6..a712c68 100644
>> --- a/migration/ram.c
>> +++ b/migration/ram.c
>> @@ -1081,7 +1081,6 @@ void migration_bitmap_extend(ram_addr_t old, ram_addr_t new)
>>            */
>>           qemu_mutex_lock(&migration_bitmap_mutex);
>>           bitmap_copy(bitmap, old_bitmap, old);
>> -        bitmap_set(bitmap, old, new - old);
>>           atomic_rcu_set(&migration_bitmap, bitmap);
>>           qemu_mutex_unlock(&migration_bitmap_mutex);
>>           migration_dirty_pages += new - old;
>> @@ -1146,7 +1145,6 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
>>   
>>       ram_bitmap_pages = last_ram_offset() >> TARGET_PAGE_BITS;
>>       migration_bitmap = bitmap_new(ram_bitmap_pages);
>> -    bitmap_set(migration_bitmap, 0, ram_bitmap_pages);
>>   
>>       /*
>>        * Count the total number of pages used by ram blocks not including any
>>