Re: [Qemu-devel] [PATCH v2 1/4] block: introduce aio task pool

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

13.08.2019 23:47, Max Reitz wrote:
> On 30.07.19 16:18, Vladimir Sementsov-Ogievskiy wrote:
>> Common interface for aio task loops. To be used for improving
>> performance of synchronous io loops in qcow2, block-stream,
>> copy-on-read, and may be other places.
>>
>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>> ---
> 
> Looks good to me overall.
> 
>>   block/aio_task.h    |  52 +++++++++++++++++++
> 
> I’ve move this to include/block/.
> 
>>   block/aio_task.c    | 119 ++++++++++++++++++++++++++++++++++++++++++++
>>   block/Makefile.objs |   2 +
>>   3 files changed, 173 insertions(+)
>>   create mode 100644 block/aio_task.h
>>   create mode 100644 block/aio_task.c
>>
>> diff --git a/block/aio_task.h b/block/aio_task.h
>> new file mode 100644
>> index 0000000000..933af1d8e7
>> --- /dev/null
>> +++ b/block/aio_task.h
> 
> [...]
> 
>> +typedef struct AioTaskPool AioTaskPool;
>> +typedef struct AioTask AioTask;
>> +typedef int (*AioTaskFunc)(AioTask *task);
> 
> +coroutine_fn
> 
>> +struct AioTask {
>> +    AioTaskPool *pool;
>> +    AioTaskFunc func;
>> +    int ret;
>> +};
>> +
>> +/*
>> + * aio_task_pool_new
>> + *
>> + * The caller is responsible to g_free AioTaskPool pointer after use.
> 
> s/to g_free/for g_freeing/ or something similar.
> 
> Or you’d just add aio_task_pool_free().
> 
>> + */
>> +AioTaskPool *aio_task_pool_new(int max_busy_tasks);
>> +int aio_task_pool_status(AioTaskPool *pool);
> 
> A comment wouldn’t hurt.  It wasn’t immediately clear to me that status
> refers to the error code of a failing task (or 0), although it wasn’t
> too much of a surprise either.
> 
>> +bool aio_task_pool_empty(AioTaskPool *pool);
>> +void aio_task_pool_start_task(AioTaskPool *pool, AioTask *task);
> 
> Maybe make a note that task->pool will be set automatically?
> 
>> +void aio_task_pool_wait_slot(AioTaskPool *pool);
>> +void aio_task_pool_wait_one(AioTaskPool *pool);
>> +void aio_task_pool_wait_all(AioTaskPool *pool);
> 
> Shouldn’t all of these but aio_task_pool_empty() and
> aio_task_pool_status() be coroutine_fns?
> 
>> +#endif /* BLOCK_AIO_TASK_H */
>> diff --git a/block/aio_task.c b/block/aio_task.c
>> new file mode 100644
>> index 0000000000..807be8deb5
>> --- /dev/null
>> +++ b/block/aio_task.c
> 
> [...]
> 
>> +static void aio_task_co(void *opaque)
> 
> +coroutine_fn
> 
> [...]
> 
>> +void aio_task_pool_wait_one(AioTaskPool *pool)
>> +{
>> +    assert(pool->busy_tasks > 0);
>> +    assert(qemu_coroutine_self() == pool->main_co);
>> +
>> +    pool->wait_done = true;
> 
> Hmmm, but the wait actually isn’t done yet. :-)
> 
> Maybe s/wait_done/waiting/?
> 


Aha, really bad variable name. I meant "wait for one task done". Just "waiting" would be appropriate.

Thanks for reviewing!

-- 
Best regards,
Vladimir