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

[zhanghailiang]

On 2015/11/14 0:19, Dr. David Alan Gilbert wrote:
> * zhanghailiang (address@hidden) 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 <address@hidden>
> > ---
> > 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 / address@hidden / Manchester, UK
>
> .