On 03/08/2024 15:39, Michael S. Tsirkin wrote:
On Sat, Aug 03, 2024 at 01:07:27AM +0300, Max Gurtovoy wrote:
On 01/08/2024 20:56, Stefan Hajnoczi wrote:
On Thu, Aug 01, 2024 at 06:56:44PM +0300, Max Gurtovoy wrote:
On 01/08/2024 18:43, Michael S. Tsirkin wrote:
On Thu, Aug 01, 2024 at 06:39:16PM +0300, Max Gurtovoy wrote:
On 01/08/2024 18:29, Michael S. Tsirkin wrote:
On Thu, Aug 01, 2024 at 06:17:21PM +0300, Max Gurtovoy wrote:
On 01/08/2024 18:13, Michael S. Tsirkin wrote:
On Thu, Aug 01, 2024 at 06:11:37PM +0300, Max Gurtovoy wrote:
In this operation set the driver data of the hctx to point to the virtio
block queue. By doing so, we can use this reference in the and reduce
in the .... ?
sorry for the type.
should be :
"By doing so, we can use this reference and reduce the number of operations in the fast path."
ok. what kind of benefit do you see with this patch?
As mentioned. This is a micro optimization that reduce the number of
instructions/dereferences in the fast path.
By how much? How random code tweaks affect object code is unpredictable.
Pls show results of objdump to prove it does anything
useful.
This is the way all modern block drivers such as NVMe PCI/RDMA/TCP use the
driver_data.
These drivers don't have driver specific mechanisms to find the queue from
the hctx->queue->queuedata like vblk driver has for some unknown reason.
It is pretty easy to review this patch and see its benefits, isn't it ?
It is not expected to provide extreme perf improvement.
It is introduced for aligning the driver to use common MQ mechanisms and
reduce dereferences.
This is not "random code tweaks".
If you cannot observe a performance change, then adjusting the commit
description to explain this as a code cleanup to reduce dereferences and
local variables, improving code readability seems fine to me. I think
it's a nice cleanup when presented as such rather than a performance
optimization.
Stefan
Sure. Please check the bellow adjustment:
virtio_blk: implement init_hctx MQ operation
Set the driver data of the hardware context (hctx) to point directly to
the virtio block queue. This cleanup improves code readability, reduces
the number of dereferences, and minimizes local variables in the fast
path.
I'd drop the local variables part, it is not at all clear why is that
a win.
We can drop it:
virtio_blk: implement init_hctx MQ operation
Set the driver data of the hardware context (hctx) to point directly to
the virtio block queue. This cleanup improves code readability and reduces
the number of dereferences in the fast path.
