Re: [Qemu-devel] [PATCH COLO-Frame v10 15/38] ram/COLO: Record pages received from PVM by re-using migration dirty bitmap

[zhanghailiang <zhang.zhanghailiang@huawei.com>]

On 2015/11/14 0:19, Dr. David Alan Gilbert wrote:
> * zhanghailiang (zhang.zhanghailiang@huawei.com) wrote:
>> We need to record the address of the dirty pages that received from PVM,
>> It will help flushing pages that cached into SVM.
>>
>> Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
>> ---
>> v10:
>> - New patch split from v9's patch 13
>> - Rebase to master to use 'migration_bitmap_rcu'
>> ---
>>   migration/ram.c | 35 +++++++++++++++++++++++++++++++++++
>>   1 file changed, 35 insertions(+)
>>
>> diff --git a/migration/ram.c b/migration/ram.c
>> index b094dc3..70879bd 100644
>> --- a/migration/ram.c
>> +++ b/migration/ram.c
>> @@ -1448,6 +1448,18 @@ static inline void *host_from_stream_offset(QEMUFile *f,
>>           }
>>
>>           if (ram_cache_enable) {
>> +            unsigned long *bitmap;
>> +            long k = (block->mr->ram_addr + offset) >> TARGET_PAGE_BITS;
>> +
>> +            bitmap = atomic_rcu_read(&migration_bitmap_rcu)->bmap;
>> +            /*
>> +            * During colo checkpoint, we need bitmap of these migrated pages.
>> +            * It help us to decide which pages in ram cache should be flushed
>> +            * into VM's RAM later.
>> +            */
>> +            if (!test_and_set_bit(k, bitmap)) {
>> +                migration_dirty_pages++;
>> +            }
>
> I don't like having this in host_from_stream_offset; if you look
> at the current ram_load there is only a single call to host_from_stream_offset, so it's
> now much easier for you to move it into a separate function.
>

Hmm, that's really a good idea, i will split it in next version.

>>               return block->host_cache + offset;
>>           } else {
>>               return block->host + offset;
>> @@ -1462,6 +1474,13 @@ static inline void *host_from_stream_offset(QEMUFile *f,
>>           if (!strncmp(id, block->idstr, sizeof(id)) &&
>>               block->max_length > offset) {
>>               if (ram_cache_enable) {
>> +                unsigned long *bitmap;
>> +                long k = (block->mr->ram_addr + offset) >> TARGET_PAGE_BITS;
>> +
>> +                bitmap = atomic_rcu_read(&migration_bitmap_rcu)->bmap;
>> +                if (!test_and_set_bit(k, bitmap)) {
>> +                    migration_dirty_pages++;
>> +                }
>>                   return block->host_cache + offset;
>>               } else {
>>                   return block->host + offset;
>> @@ -1723,6 +1742,7 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
>>   int colo_init_ram_cache(void)
>>   {
>>       RAMBlock *block;
>> +    int64_t ram_cache_pages = last_ram_offset() >> TARGET_PAGE_BITS;
>>
>>       rcu_read_lock();
>>       QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
>> @@ -1734,6 +1754,15 @@ int colo_init_ram_cache(void)
>>       }
>>       rcu_read_unlock();
>>       ram_cache_enable = true;
>> +    /*
>> +    * Record the dirty pages that sent by PVM, we use this dirty bitmap together
>> +    * with to decide which page in cache should be flushed into SVM's RAM. Here
>> +    * we use the same name 'migration_bitmap_rcu' as for migration.
>> +    */
>> +    migration_bitmap_rcu = g_new(struct BitmapRcu, 1);
>
> Please update that to g_new0 (I changed the other use when I added postcopy).
>

OK, thanks.

> Dave
>
>> +    migration_bitmap_rcu->bmap = bitmap_new(ram_cache_pages);
>> +    migration_dirty_pages = 0;
>> +
>>       return 0;
>>
>>   out_locked:
>> @@ -1751,9 +1780,15 @@ out_locked:
>>   void colo_release_ram_cache(void)
>>   {
>>       RAMBlock *block;
>> +    struct BitmapRcu *bitmap = migration_bitmap_rcu;
>>
>>       ram_cache_enable = false;
>>
>> +    atomic_rcu_set(&migration_bitmap_rcu, NULL);
>> +    if (bitmap) {
>> +        call_rcu(bitmap, migration_bitmap_free, rcu);
>> +    }
>> +
>>       rcu_read_lock();
>>       QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
>>           if (block->host_cache) {
>> --
>> 1.8.3.1
>>
>>
> --
> Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
>
> .
>