levelcrow
Posts: 47
Joined: Tue Aug 12, 2014 5:04 pm

How accelerated is Raspbian?

Sun Apr 03, 2016 2:32 am

Eric Anholt has been working on getting full OpenGL working on the Raspberry Pi. One of the big improvements I have been anticipating is a fully accelerated desktop environment through Glamor. I'm not an expert or even a hobbyist by any means regarding GPU acceleration, but I often think about how the acceleration might improve Raspbian performance - perhaps because I find it interesting in regards to how important software is in terms of hardware performance, and also because I used to use the Raspberry Pi 1B as a main computer but found it just a little bit too slow.

I know that some hardware acceleration has already been implemented - smooth window dragging and resizing has been around for a while. However, I also know that the task manager shows CPU usage for processes as the cursor runs over their windows.

My question is: could anyone give me a rough estimate as to how accelerated the desktop environment with the current version of Raspbian is? Is it unreasonable to expect significant improvements in the future - has most of the basic stuff already been accelerated? Or is a not-insignificant performance bump in the horizon for the Raspberry Pi 1/0 desktop experience?

W. H. Heydt
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Re: How accelerated is Raspbian?

Sun Apr 03, 2016 3:16 am

I believe that Arnholt's work is slated to be included in the Linux source tree quite soon, such as an upcoming release or two from now. *Part* of the work on the VC4 is, apparently, already in the kernel source tree (Rel. 4.4? 4.5?). My knowledge of where is this is at is from secondary--or tertiary--sources. If you want to know with more certainty, you should probaly do a web search and/or start reading Linux systems groups.

levelcrow
Posts: 47
Joined: Tue Aug 12, 2014 5:04 pm

Re: How accelerated is Raspbian?

Sun Apr 03, 2016 4:05 am

I think I read a fairly recent post on Reddit by Eric Anholt detailing that desktop environment acceleration is going to need a not-insignificant implementation of render acceleration in Glamor.

I've been following his Git activity over the past couple months, it looks like he has been focusing on panel compatibility in regards to the currently available OpenGL driver. He has a bunch of issues open regarding stability and output compatibility, and so I anticipate it's going to be at least a month or two before there's serious work on Glamor. In addition to this, it's not quite clear when Raspbian is going to release the OpenGL drivers for the Raspberry Pi 1/0. According to Eric Anholt, the compatibility is there - the current OpenGL drivers were developed on the 2835. I'm sure there's a good reason for the unavailability of the driver and I'm guessing it will eventually be released for the Pi1/0 as stability and features improve. However, it means that there's going to be even more work and time beyond Eric Anholt's contributions before the OpenGL - and Glamor implementation - hit Raspbian for the Raspberry Pi 1/0. Though the drivers should work with upstream kernels, I anticipate that the Raspberry PI 1/0 would have a significant performance decrease with non-Raspbian as they are ARMv6.

I've searched to try to figure out exactly how accelerated the current Raspbian is, but I don't have the technical knowledge or expertise to make a good guess - nor have I come across a good estimate. There seems to be a clear separation of those in-the-know and those not in-the-know, and those in-the-know seem to think there's improvements that can be made - though to what and how much I do not know. I do know that the Foundation was working with Collabora on Maynard and setting up a switch to Wayland back in 2014, though this seems to have frozen. Really, I'm looking for a rough estimate - like "the GPU is not used 30% of the time it could be" - or perhaps a basic explanation regarding what could change or a comparison between Raspbian in its current state and Debian on other hardware using Glamor or EXA.

A visit from Eric Anholt or Simon Hall to this topic would be cool. :D

ghans
Posts: 7891
Joined: Mon Dec 12, 2011 8:30 pm
Location: Germany

Re: How accelerated is Raspbian?

Sun Apr 03, 2016 8:42 am

I think most optimizations to Debian already
happenend in 2013 - since modern X11 seems to
copy things around for the most time the optimized
memcpy must have had an measurable impact.

The Raspbian project itself was a massive improvement over
Debian "armel".

Furthermore the pixman library was also optimized for
the Pi as far i can recall.


ghans
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jamesh
Raspberry Pi Engineer & Forum Moderator
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Re: How accelerated is Raspbian?

Sun Apr 03, 2016 8:49 am

levelcrow wrote:I think I read a fairly recent post on Reddit by Eric Anholt detailing that desktop environment acceleration is going to need a not-insignificant implementation of render acceleration in Glamor.

I've been following his Git activity over the past couple months, it looks like he has been focusing on panel compatibility in regards to the currently available OpenGL driver. He has a bunch of issues open regarding stability and output compatibility, and so I anticipate it's going to be at least a month or two before there's serious work on Glamor. In addition to this, it's not quite clear when Raspbian is going to release the OpenGL drivers for the Raspberry Pi 1/0. According to Eric Anholt, the compatibility is there - the current OpenGL drivers were developed on the 2835. I'm sure there's a good reason for the unavailability of the driver and I'm guessing it will eventually be released for the Pi1/0 as stability and features improve. However, it means that there's going to be even more work and time beyond Eric Anholt's contributions before the OpenGL - and Glamor implementation - hit Raspbian for the Raspberry Pi 1/0. Though the drivers should work with upstream kernels, I anticipate that the Raspberry PI 1/0 would have a significant performance decrease with non-Raspbian as they are ARMv6.

I've searched to try to figure out exactly how accelerated the current Raspbian is, but I don't have the technical knowledge or expertise to make a good guess - nor have I come across a good estimate. There seems to be a clear separation of those in-the-know and those not in-the-know, and those in-the-know seem to think there's improvements that can be made - though to what and how much I do not know. I do know that the Foundation was working with Collabora on Maynard and setting up a switch to Wayland back in 2014, though this seems to have frozen. Really, I'm looking for a rough estimate - like "the GPU is not used 30% of the time it could be" - or perhaps a basic explanation regarding what could change or a comparison between Raspbian in its current state and Debian on other hardware using Glamor or EXA.

A visit from Eric Anholt or Simon Hall to this topic would be cool. :D
I think the reason the Pi1 isn't supported is memory, since that is the only real difference in this area. The VC4 is the same in all Pi models.

Maynard dev is frozen, the Anholt work may make it unnecessary.
Principal Software Engineer at Raspberry Pi Ltd.
Working in the Applications Team.

6by9
Raspberry Pi Engineer & Forum Moderator
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Re: How accelerated is Raspbian?

Sun Apr 03, 2016 12:56 pm

jamesh wrote:I think the reason the Pi1 isn't supported is memory, since that is the only real difference in this area. The VC4 is the same in all Pi models
The rendering side is identical, but it's the setup stuff that can be quite processor intensive. Shader compilers and the like.
Pi1 has less grunt than the vpu for that, hence the architecture that is in use. Pi2/3 the reverse is true, but supporting two stacks would be a lot more work. At least with Eric's stack as the second one it's all open source.
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