DRM Synchronization Object Improvements Queued For Linux 4.14

[phoronix]

Phoronix: DRM Synchronization Object Improvements Queued For Linux 4.14

Introduced in the Linux 4.13 kernel for the Direct Rendering Manager drivers was the concept of DRM synchronization objects while for Linux 4.14 this feature will be improved upon...

http://www.phoronix.com/scan.php?page=news_item&px=DRM-Sync-Objects-4.14

[tildearrow]

Typo:

among some otheri mprovements now in DRM-Next Git.

[suberimakuri]

Typo:

I knew the one and only comment would be you and about that!

[JPFSanders]

I struggle to understand what fences are about, or why are they desirable, I haven't found a layman explanation anywhere only technical explanations, but nothing that explains why are they used and for what reason, only that the concept seems to come from Android.

Any kind soul that could explain this to me please?

[ssam]

I struggle to understand what fences are about, or why are they desirable, I haven't found a layman explanation anywhere only technical explanations, but nothing that explains why are they used and for what reason, only that the concept seems to come from Android.

Any kind soul that could explain this to me please?

So suppose you see a process that's flush with some nice objects, and you get a window of opportunity, now they ain't stolen they've just not been paid for but it can be hard to find a good customer, but you know this guy who works a warehouse, and he's pretty good at spinning the "fell of the back of a lorry" line to people. He is your fence.

[JPFSanders]

So suppose you see a process that's flush with some nice objects, and you get a window of opportunity, now they ain't stolen they've just not been paid for but it can be hard to find a good customer, but you know this guy who works a warehouse, and he's pretty good at spinning the "fell of the back of a lorry" line to people. He is your fence.

Very funny.

Unless I'm very thick (Which I do not discount) I fail to see the relation of "Fence" related to stolen goods, with anything to do with "Fencing" in a graphics content, I understand that Fencing has to do with boundaries but I do not understand them in graphics terms, does it mean that the Fence acts like a broker of some kind?

[ssam]

Very funny.

:-)

Really I think its type of memory barrier. https://en.wikipedia.org/wiki/Memory_barrier . Maybe someone cleverer can explain if there is a difference between a barrier and a fence.

[agd5f]

A fence is a synchronization mechanism between multiple processors. E.g., the CPU and the GPU. Work is submitted to the GPU and one or more fences are associated with that work. The GPU writes values to those fences when it gets to specific points in it's pipeline. The CPU can then check the fences to see where the GPU is. For example, when the GPU is updating a frame of a game, you might have a fence associated with the GPU's completion of rendering of that frame. The driver (CPU) can then query the fence and and determine if the GPU has completed the work before it points the display engine at that new frame to avoid tearing.

[TheOne]

If thats the case it would be great to see X making use of this

[JPFSanders]

A fence is a synchronization mechanism between multiple processors. E.g., the CPU and the GPU. Work is submitted to the GPU and one or more fences are associated with that work. The GPU writes values to those fences when it gets to specific points in it's pipeline. The CPU can then check the fences to see where the GPU is. For example, when the GPU is updating a frame of a game, you might have a fence associated with the GPU's completion of rendering of that frame. The driver (CPU) can then query the fence and and determine if the GPU has completed the work before it points the display engine at that new frame to avoid tearing.

Thank you so much for the explanation, maybe my google-fu is not as good as it should be but I hadn't managed to find an explanation of what it was, the term was popping out more and more but nowhere could find an explanation.

Thanks again.