Re: [Qemu-devel] [PATCH RESEND v2 07/18] COLO: Load dirty pages into SVM's RAM cache firstly

[Juan Quintela]

zhanghailiang <address@hidden> wrote:
> We should not load PVM's state directly into SVM, because there maybe some
> errors happen when SVM is receving data, which will break SVM.
>
> We need to ensure receving all data before load the state into SVM. We use
> an extra memory to cache these data (PVM's ram). The ram cache in secondary 
> side
> is initially the same as SVM/PVM's memory. And in the process of checkpoint,
> we cache the dirty pages of PVM into this ram cache firstly, so this ram cache
> always the same as PVM's memory at every checkpoint, then we flush this 
> cached ram
> to SVM after we receive all PVM's state.
>
> Cc: Dr. David Alan Gilbert <address@hidden>
> Signed-off-by: zhanghailiang <address@hidden>
> Signed-off-by: Li Zhijian <address@hidden>
> ---
> v2:
> - Move colo_init_ram_cache() and colo_release_ram_cache() out of
>   incoming thread since both of them need the global lock, if we keep
>   colo_release_ram_cache() in incoming thread, there are potential
>   dead-lock.
> - Remove bool ram_cache_enable flag, use migration_incoming_in_state() 
> instead.
> - Remove the Reviewd-by tag because of the above changes.


> +out_locked:
> +    QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
> +        if (block->colo_cache) {
> +            qemu_anon_ram_free(block->colo_cache, block->used_length);
> +            block->colo_cache = NULL;
> +        }
> +    }
> +
> +    rcu_read_unlock();
> +    return -errno;
> +}
> +
> +/* It is need to hold the global lock to call this helper */
> +void colo_release_ram_cache(void)
> +{
> +    RAMBlock *block;
> +
> +    rcu_read_lock();
> +    QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
> +        if (block->colo_cache) {
> +            qemu_anon_ram_free(block->colo_cache, block->used_length);
> +            block->colo_cache = NULL;
> +        }
> +    }
> +    rcu_read_unlock();
> +}

Create a function from the creation/removal?  We have exactly two copies
of the same code.  Right now the code inside the function is very small,
but it could be bigger, no?

Later, Juan.