Re: [Qemu-devel] [PATCH COLO-Frame v11 15/39] COLO: Load PVM's dirty pages into SVM's RAM cache temporarily

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

On 2015/12/2 3:02, Dr. David Alan Gilbert wrote:
> * zhanghailiang (zhang.zhanghailiang@huawei.com) 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.
>>
>> Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
>> Signed-off-by: Li Zhijian <lizhijian@cn.fujitsu.com>
>> Signed-off-by: Gonglei <arei.gonglei@huawei.com>
>> ---
>> v11:
>> - Rename 'host_cache' to 'colo_cache' (Dave's suggestion)
>> v10:
>> - Split the process of dirty pages recording into a new patch
>> ---
>>   include/exec/ram_addr.h       |  1 +
>>   include/migration/migration.h |  4 +++
>>   migration/colo.c              | 10 +++++++
>>   migration/ram.c               | 69 ++++++++++++++++++++++++++++++++++++++++++-
>>   4 files changed, 83 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
>> index 7115154..bb44f66 100644
>> --- a/include/exec/ram_addr.h
>> +++ b/include/exec/ram_addr.h
>> @@ -26,6 +26,7 @@ struct RAMBlock {
>>       struct rcu_head rcu;
>>       struct MemoryRegion *mr;
>>       uint8_t *host;
>> +    uint8_t *colo_cache; /* For colo, VM's ram cache */
>>       ram_addr_t offset;
>>       ram_addr_t used_length;
>>       ram_addr_t max_length;
>> diff --git a/include/migration/migration.h b/include/migration/migration.h
>> index ba5bcec..e41372d 100644
>> --- a/include/migration/migration.h
>> +++ b/include/migration/migration.h
>> @@ -332,4 +332,8 @@ int ram_save_queue_pages(MigrationState *ms, const char *rbname,
>>   PostcopyState postcopy_state_get(void);
>>   /* Set the state and return the old state */
>>   PostcopyState postcopy_state_set(PostcopyState new_state);
>> +
>> +/* ram cache */
>> +int colo_init_ram_cache(void);
>> +void colo_release_ram_cache(void);
>>   #endif
>> diff --git a/migration/colo.c b/migration/colo.c
>> index 012d8e5..6e933fa 100644
>> --- a/migration/colo.c
>> +++ b/migration/colo.c
>> @@ -304,6 +304,12 @@ void *colo_process_incoming_thread(void *opaque)
>>       qemu_set_block(qemu_get_fd(mis->from_src_file));
>>
>>
>> +    ret = colo_init_ram_cache();
>> +    if (ret < 0) {
>> +        error_report("Failed to initialize ram cache");
>> +        goto out;
>> +    }
>> +
>>       ret = colo_ctl_put(mis->to_src_file, COLO_COMMAND_CHECKPOINT_READY, 0);
>>       if (ret < 0) {
>>           goto out;
>> @@ -353,6 +359,10 @@ out:
>>                        strerror(-ret));
>>       }
>>
>> +    qemu_mutex_lock_iothread();
>> +    colo_release_ram_cache();
>> +    qemu_mutex_unlock_iothread();
>> +
>>       if (mis->to_src_file) {
>>           qemu_fclose(mis->to_src_file);
>>       }
>> diff --git a/migration/ram.c b/migration/ram.c
>> index a161620..9d946a1 100644
>> --- a/migration/ram.c
>> +++ b/migration/ram.c
>> @@ -223,6 +223,7 @@ static RAMBlock *last_sent_block;
>>   static ram_addr_t last_offset;
>>   static QemuMutex migration_bitmap_mutex;
>>   static uint64_t migration_dirty_pages;
>> +static bool ram_cache_enable;
>>   static uint32_t last_version;
>>   static bool ram_bulk_stage;
>>
>> @@ -2175,6 +2176,16 @@ static inline void *host_from_ram_block_offset(RAMBlock *block,
>>       return block->host + offset;
>>   }
>>
>> +static inline void *colo_cache_from_block_offset(RAMBlock *block,
>> +                                                 ram_addr_t offset)
>> +{
>> +    if (!block) {
>> +        return NULL;
>> +    }
>> +
>> +    return block->colo_cache + offset;
>> +}
>> +
>>   /*
>>    * If a page (or a whole RDMA chunk) has been
>>    * determined to be zero, then zap it.
>> @@ -2454,7 +2465,12 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
>>                        RAM_SAVE_FLAG_COMPRESS_PAGE | RAM_SAVE_FLAG_XBZRLE)) {
>>               RAMBlock *block = ram_block_from_stream(f, addr, flags);
>>
>> -            host = host_from_ram_block_offset(block, addr);
>> +            /* After going into COLO, we should load the Page into colo_cache */
>> +            if (ram_cache_enable) {
>> +                host = colo_cache_from_block_offset(block, addr);
>> +            } else {
>> +                host = host_from_ram_block_offset(block, addr);
>> +            }
>>               if (!host) {
>>                   error_report("Illegal RAM offset " RAM_ADDR_FMT, addr);
>>                   ret = -EINVAL;
>> @@ -2550,6 +2566,57 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
>>       return ret;
>>   }
>>
>> +/*
>> + * colo cache: this is for secondary VM, we cache the whole
>> + * memory of the secondary VM, it will be called after first migration.
>> + */
>> +int colo_init_ram_cache(void)
>> +{
>> +    RAMBlock *block;
>> +
>> +    rcu_read_lock();
>> +    QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
>> +        block->colo_cache = qemu_anon_ram_alloc(block->used_length, NULL);
>> +        if (!block->colo_cache) {
>> +            error_report("%s: Can't alloc memory for colo cache of block %s,"
>> +                         "size %zu", __func__, block->idstr,
>> +                         block->used_length);
>
> Minor one that I didn't spot before;  I think that has to be RAM_ADDR_FMT instead of %zu
>

OK, i will fix it, thanks.

> However, other than that;
>
> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
>
> Dave
>
>> +            goto out_locked;
>> +        }
>> +        memcpy(block->colo_cache, block->host, block->used_length);
>> +    }
>> +    rcu_read_unlock();
>> +    ram_cache_enable = true;
>> +    return 0;
>> +
>> +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;
>> +}
>> +
>> +void colo_release_ram_cache(void)
>> +{
>> +    RAMBlock *block;
>> +
>> +    ram_cache_enable = false;
>> +
>> +    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();
>> +}
>> +
>>   static SaveVMHandlers savevm_ram_handlers = {
>>       .save_live_setup = ram_save_setup,
>>       .save_live_iterate = ram_save_iterate,
>> --
>> 1.8.3.1
>>
>>
> --
> Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
>
> .
>