On Tue, Jul 1, 2014 at 7:18 PM, Kevin Wolf <kw...@redhat.com> wrote:
> Am 01.07.2014 um 09:51 hat Ming Lei geschrieben:
>> This patch introduces these two APIs so that following
>> patches can support queuing I/O requests and submitting them
>> at batch for improving I/O performance.
>>
>> Reviewed-by: Paolo Bonzini <pbonz...@redhat.com>
>> Signed-off-by: Ming Lei <ming....@canonical.com>
>> ---
>> block.c | 21 +++++++++++++++++++++
>> include/block/block.h | 3 +++
>> include/block/block_int.h | 4 ++++
>> 3 files changed, 28 insertions(+)
>>
>> diff --git a/block.c b/block.c
>> index 217f523..fea9e43 100644
>> --- a/block.c
>> +++ b/block.c
>> @@ -1910,6 +1910,7 @@ void bdrv_drain_all(void)
>> bool bs_busy;
>>
>> aio_context_acquire(aio_context);
>> + bdrv_io_unplug(bs);
>> bdrv_start_throttled_reqs(bs);
>> bs_busy = bdrv_requests_pending(bs);
>> bs_busy |= aio_poll(aio_context, bs_busy);
>
> This means that bdrv_io_plug/unplug() are not paired as I would have
> expected. I find the name not very descriptive anyway (I probably
> wouldn't have guessed what it does from its name if it weren't in this
> series), so maybe we should consider renaming it?
>
> Perhaps something like bdrv_req_batch_start() and
> bdrv_req_batch_submit(), but I'm open for different suggestions.
The term of plug/unplug have been used in block subsystem of
linux kernel for long time, just like pipe with faucet, :-)
>> @@ -5774,3 +5775,23 @@ bool bdrv_is_first_non_filter(BlockDriverState
>> *candidate)
>>
>> return false;
>> }
>> +
>> +void bdrv_io_plug(BlockDriverState *bs)
>> +{
>> + BlockDriver *drv = bs->drv;
>> + if (drv && drv->bdrv_io_plug) {
>> + drv->bdrv_io_plug(bs);
>> + } else if (bs->file) {
>> + bdrv_io_plug(bs->file);
>> + }
>> +}
>
> Does this bs->file forwarding work for more than the raw driver? For
> example, if drv is an image format driver that needs to read some
> metadata from the image before it can submit the payload, does this
> still do what you were intending?
Yes, I think so, even though the current implementation is just for
"fixing" dataplane and keeping simple as far as possible, because
reading both metadata and payload will forward to bs->file, and
bs->file->drv should have supported plug & unplug in case of
linux-aio.
Thanks,
--
Ming Lei
