Hi, Oak.
On 1/4/22 00:08, Zeng, Oak wrote:
Regards,
Oak
Looks like your emails always start with "Regards, Oak". a misconfiguration?
-----Original Message-----
From: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
Sent: January 3, 2022 1:58 PM
To: Zeng, Oak <oak.zeng@xxxxxxxxx>; intel-gfx@xxxxxxxxxxxxxxxxxxxxx; dri-devel@xxxxxxxxxxxxxxxxxxxxx
Cc: Auld, Matthew <matthew.auld@xxxxxxxxx>
Subject: Re: [PATCH v4 2/4] drm/i915: Use the vma resource as argument for gtt binding / unbinding
Hi, Oak.
On 1/3/22 19:17, Zeng, Oak wrote:
Regards,
Oak
-----Original Message-----
From: Intel-gfx <intel-gfx-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf Of Thomas Hellström
Sent: January 3, 2022 7:00 AM
To: intel-gfx@xxxxxxxxxxxxxxxxxxxxx; dri-devel@xxxxxxxxxxxxxxxxxxxxx
Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>; Auld, Matthew <matthew.auld@xxxxxxxxx>
Subject: [PATCH v4 2/4] drm/i915: Use the vma resource as argument for gtt binding / unbinding
When introducing asynchronous unbinding, the vma itself may no longer
be alive when the actual binding or unbinding takes place.
Can we take an extra reference counter of the vma to keep the vma alive, until the actual binding/unbinding takes place?
The point here is that that's not needed, and should be avoided.
Can you explain more why "keeping vma alive until unbinding takes place" should be avoided?
As I understand it, your series introduce asynchronized unbinding. But since vma might be no longer alive at the time of unbinding. To overcome this difficulty, you introduce a vma resource structure and you guarantee vma resource is alive at bind/unbind time. So you can use vma resource for the bind/unbind operation. My question is, can we achieve the asynchronized unbinding still using vma structure by keeping vma structure alive ( by ref count it). This way the change should be much smaller (compared to this series). Why it is harmful to keep the vma alive? Maybe you have other reasons to introduce vma resource that I don't see.
When we allow asynchronous unbinding, it's allowed to immediately rebind
the vma, possibly into the same gpu virtual address, but with different
pages. And when doing that we don't want to block waiting for the unbind
to execute. In fact, we could allow a large number of outstanding binds
and unbinds for a vma, which makes the vma structure unsuitable to track
this, since there will no longer be a single mapping between a set of
active pages and a vma, or a virtual gpu range and a vma.
Thanks,
/Thomas
Regards,
Oak
If the
vma is no longer alive, that means nobody uses it anymore, but the GPU
may still have work in the pipe that references the GPU virtual address.
/Thomas.
