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

[Max Reitz <mreitz@redhat.com>]

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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/?

Max

> +    qemu_coroutine_yield();
> +
> +    assert(!pool->wait_done);
> +    assert(pool->busy_tasks < pool->max_busy_tasks);
> +}


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