Am 14.01.21 um 20:19 schrieb Jason Dillaman:
> On Sun, Dec 27, 2020 at 11:42 AM Peter Lieven <p...@kamp.de> wrote:
>> Signed-off-by: Peter Lieven <p...@kamp.de>
>> ---
>> block/rbd.c | 31 ++++++++++++++++++++++++++++++-
>> 1 file changed, 30 insertions(+), 1 deletion(-)
>>
>> diff --git a/block/rbd.c b/block/rbd.c
>> index 2d77d0007f..27b4404adf 100644
>> --- a/block/rbd.c
>> +++ b/block/rbd.c
>> @@ -63,7 +63,8 @@ typedef enum {
>> RBD_AIO_READ,
>> RBD_AIO_WRITE,
>> RBD_AIO_DISCARD,
>> - RBD_AIO_FLUSH
>> + RBD_AIO_FLUSH,
>> + RBD_AIO_WRITE_ZEROES
>> } RBDAIOCmd;
>>
>> typedef struct BDRVRBDState {
>> @@ -221,8 +222,12 @@ done:
>>
>> static void qemu_rbd_refresh_limits(BlockDriverState *bs, Error **errp)
>> {
>> + BDRVRBDState *s = bs->opaque;
>> /* XXX Does RBD support AIO on less than 512-byte alignment? */
>> bs->bl.request_alignment = 512;
>> +#ifdef LIBRBD_SUPPORTS_WRITE_ZEROES
>> + bs->bl.pwrite_zeroes_alignment = s->object_size;
> The optimal alignment is 512 bytes -- but it can safely work just fine
> down to 1 byte alignment since it will pad the request with additional
> writes if needed.
Okay and this will likely be faster than having Qemu doing that request split,
right?
If we drop the alignment hint Qemu will pass the original request.
>
>> +#endif
>> }
>>
>>
>> @@ -695,6 +700,9 @@ static int qemu_rbd_open(BlockDriverState *bs, QDict
>> *options, int flags,
>> }
>>
>> s->aio_context = bdrv_get_aio_context(bs);
>> +#ifdef LIBRBD_SUPPORTS_WRITE_ZEROES
>> + bs->supported_zero_flags = BDRV_REQ_MAY_UNMAP;
>> +#endif
>>
>> /* When extending regular files, we get zeros from the OS */
>> bs->supported_truncate_flags = BDRV_REQ_ZERO_WRITE;
>> @@ -808,6 +816,11 @@ static int coroutine_fn
>> qemu_rbd_start_co(BlockDriverState *bs,
>> case RBD_AIO_FLUSH:
>> r = rbd_aio_flush(s->image, c);
>> break;
>> +#ifdef LIBRBD_SUPPORTS_WRITE_ZEROES
>> + case RBD_AIO_WRITE_ZEROES:
>> + r = rbd_aio_write_zeroes(s->image, offset, bytes, c, 0, 0);
>> + break;
>> +#endif
>> default:
>> r = -EINVAL;
>> }
>> @@ -880,6 +893,19 @@ static int coroutine_fn
>> qemu_rbd_co_pdiscard(BlockDriverState *bs,
>> return qemu_rbd_start_co(bs, offset, count, NULL, 0, RBD_AIO_DISCARD);
>> }
>>
>> +#ifdef LIBRBD_SUPPORTS_WRITE_ZEROES
>> +static int
>> +coroutine_fn qemu_rbd_co_pwrite_zeroes(BlockDriverState *bs, int64_t offset,
>> + int count, BdrvRequestFlags flags)
>> +{
>> + if (!(flags & BDRV_REQ_MAY_UNMAP)) {
>> + return -ENOTSUP;
>> + }
> There is a "RBD_WRITE_ZEROES_FLAG_THICK_PROVISION" flag that you can
> use to optionally disable unmap.
I have seen that. If you want I can support for this, too. But afaik this
is only available since Octopus release?
Peter
