[opensuse-arm] CONFIG_PREEMPT for ARM boards?

newer
[opensuse-arm] Using DSP in OMAP4...

Guillaume Gardet

11 Oct 2012 11 Oct '12

15:45

Hi, Does anybody thought about kernel preemption for ARM boards? It could be usefull since kernel preemption is intended to embedded system or (Low-latency) Desktop. Moreover, If we want to enable openGL on omap4 (pandaboard), we need a preemptible kernel. Is there any objection to move to a preemptible kernel for omap2plus? For other ARM boards? For Factory and/or 12.2? Guillaume -- To unsubscribe, e-mail: opensuse-arm+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-arm+owner@opensuse.org

Show replies by date

Alexander Graf

11 Oct 11 Oct

15:47

On 11.10.2012, at 17:45, Guillaume Gardet wrote:

...

Hi,

Does anybody thought about kernel preemption for ARM boards? It could be usefull since kernel preemption is intended to embedded system or (Low-latency) Desktop.

Moreover, If we want to enable openGL on omap4 (pandaboard), we need a preemptible kernel.

Why?

...

Is there any objection to move to a preemptible kernel for omap2plus? For other ARM boards? For Factory and/or 12.2?

It usually incurs overhead for not too much perceivable gain. Have you run into latency issues? Alex -- To unsubscribe, e-mail: opensuse-arm+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-arm+owner@opensuse.org

Andrew Wafaa

15:50

On 11 October 2012 16:47, Alexander Graf wrote:

...

On 11.10.2012, at 17:45, Guillaume Gardet wrote:

...
Hi,

Does anybody thought about kernel preemption for ARM boards? It could be usefull since kernel preemption is intended to embedded system or (Low-latency) Desktop.

Moreover, If we want to enable openGL on omap4 (pandaboard), we need a preemptible kernel.

Why?

...
Is there any objection to move to a preemptible kernel for omap2plus? For other ARM boards? For Factory and/or 12.2?

It usually incurs overhead for not too much perceivable gain. Have you run into latency issues?

Alex

-- To unsubscribe, e-mail: opensuse-arm+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-arm+owner@opensuse.org

I would love to see a PreemptRT kernel for openSUSE ARM, mostly as I am doing more PREEMPT_RT work, and it would also be useful for seeing how much of CGL we could comply with. For fear of adding _more_ kernels, could we not have RT kernels in addition to the regular ones - so have say a kernel-omap2plus and a kernel-rt-omap2plus etc? -- Andrew Wafaa IRC: FunkyPenguin GPG: 0x3A36312F -- To unsubscribe, e-mail: opensuse-arm+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-arm+owner@opensuse.org

Alexander Graf

15:52

On 11.10.2012, at 17:50, Andrew Wafaa wrote:

...

On 11 October 2012 16:47, Alexander Graf wrote:

...
On 11.10.2012, at 17:45, Guillaume Gardet wrote:

...
Hi,

Does anybody thought about kernel preemption for ARM boards? It could be usefull since kernel preemption is intended to embedded system or (Low-latency) Desktop.

Moreover, If we want to enable openGL on omap4 (pandaboard), we need a preemptible kernel.

Why?

...
Is there any objection to move to a preemptible kernel for omap2plus? For other ARM boards? For Factory and/or 12.2?

It usually incurs overhead for not too much perceivable gain. Have you run into latency issues?

Alex

-- To unsubscribe, e-mail: opensuse-arm+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-arm+owner@opensuse.org

I would love to see a PreemptRT kernel for openSUSE ARM, mostly as I am doing more PREEMPT_RT work, and it would also be useful for seeing how much of CGL we could comply with. For fear of adding _more_ kernels, could we not have RT kernels in addition to the regular ones - so have say a kernel-omap2plus and a kernel-rt-omap2plus etc?

I'd like to postpone that until we actually can have a -default kernel. Adding a -desktop and -rt flavor would be ok with me by then. But having n*x kernels just doesn't scale well. Alex -- To unsubscribe, e-mail: opensuse-arm+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-arm+owner@opensuse.org

Andrew Wafaa

16:13

On 11 October 2012 16:52, Alexander Graf wrote:

...

On 11.10.2012, at 17:50, Andrew Wafaa wrote:

...
On 11 October 2012 16:47, Alexander Graf wrote:

...
On 11.10.2012, at 17:45, Guillaume Gardet wrote:

...
Hi,

Does anybody thought about kernel preemption for ARM boards? It could be usefull since kernel preemption is intended to embedded system or (Low-latency) Desktop.

Moreover, If we want to enable openGL on omap4 (pandaboard), we need a preemptible kernel.

Why?

...
Is there any objection to move to a preemptible kernel for omap2plus? For other ARM boards? For Factory and/or 12.2?

It usually incurs overhead for not too much perceivable gain. Have you run into latency issues?

Alex

-- To unsubscribe, e-mail: opensuse-arm+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-arm+owner@opensuse.org

I would love to see a PreemptRT kernel for openSUSE ARM, mostly as I am doing more PREEMPT_RT work, and it would also be useful for seeing how much of CGL we could comply with. For fear of adding _more_ kernels, could we not have RT kernels in addition to the regular ones - so have say a kernel-omap2plus and a kernel-rt-omap2plus etc?

I'd like to postpone that until we actually can have a -default kernel. Adding a -desktop and -rt flavor would be ok with me by then. But having n*x kernels just doesn't scale well.

Alex

So until there's a unified zImage? That won't be until 3.7 at the earliest, even then it will be for a subset of vendors. It makes sense, just that it isn't that near term. I suppose there's no reason that we couldn't have PREEMPT_RT in a home repo in the mean time. -- Andrew Wafaa IRC: FunkyPenguin GPG: 0x3A36312F -- To unsubscribe, e-mail: opensuse-arm+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-arm+owner@opensuse.org

guillaume.gardet＠free.fr

16:46

New subject: Re : Re: [opensuse-arm] CONFIG_PREEMPT for ARM boards?

----- Alexander Graf a écrit :

...

On 11.10.2012, at 17:45, Guillaume Gardet wrote:

...
Hi,

Does anybody thought about kernel preemption for ARM boards? It could be usefull since kernel preemption is intended to embedded system or (Low-latency) Desktop.

Moreover, If we want to enable openGL on omap4 (pandaboard), we need a preemptible kernel.

Why?

It is a build requirement, otherwise, we get: [ 664s] /home/abuild/rpmbuild/BUILD/pvr-omap4-kernel-1330667111/sgx/eurasiacon/binary2_omap4430_linux_release/target/kbuild/services4/srvkm/env/linux/osfunc.c:85:2: error: #error "A preemptible Linux kernel is required when using workqueues"

...

...
Is there any objection to move to a preemptible kernel for omap2plus? For other ARM boards? For Factory and/or 12.2?

It usually incurs overhead for not too much perceivable gain. Have you run into latency issues?

No, but it may be useful for people using sound or things like that which need low latency. Guillaume

...

Alex

-- To unsubscribe, e-mail: opensuse-arm+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-arm+owner@opensuse.org

Alexander Graf

20:14

On 11.10.2012, at 18:46, guillaume.gardet@free.fr wrote:

...

----- Alexander Graf a écrit :

...
On 11.10.2012, at 17:45, Guillaume Gardet wrote:

...
Hi,

Does anybody thought about kernel preemption for ARM boards? It could be usefull since kernel preemption is intended to embedded system or (Low-latency) Desktop.

Moreover, If we want to enable openGL on omap4 (pandaboard), we need a preemptible kernel.

Why?

It is a build requirement, otherwise, we get: [ 664s] /home/abuild/rpmbuild/BUILD/pvr-omap4-kernel-1330667111/sgx/eurasiacon/binary2_omap4430_linux_release/target/kbuild/services4/srvkm/env/linux/osfunc.c:85:2: error: #error "A preemptible Linux kernel is required when using workqueues"

That sounds very very wrong :).

...

...
...
Is there any objection to move to a preemptible kernel for omap2plus? For other ARM boards? For Factory and/or 12.2?

It usually incurs overhead for not too much perceivable gain. Have you run into latency issues?

No, but it may be useful for people using sound or things like that which need low latency.

Well, we can switch _all_ our kernels to PREEMPT_VOLUNTARY. Alex -- To unsubscribe, e-mail: opensuse-arm+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-arm+owner@opensuse.org

Guillaume Gardet

12 Oct 12 Oct

09:36

Le 11/10/2012 22:14, Alexander Graf a écrit :

...

On 11.10.2012, at 18:46, guillaume.gardet@free.fr wrote:

...
----- Alexander Graf a écrit :

...
On 11.10.2012, at 17:45, Guillaume Gardet wrote:

...
Hi,

Does anybody thought about kernel preemption for ARM boards? It could be usefull since kernel preemption is intended to embedded system or (Low-latency) Desktop.

Moreover, If we want to enable openGL on omap4 (pandaboard), we need a preemptible kernel. Why? It is a build requirement, otherwise, we get: [ 664s] /home/abuild/rpmbuild/BUILD/pvr-omap4-kernel-1330667111/sgx/eurasiacon/binary2_omap4430_linux_release/target/kbuild/services4/srvkm/env/linux/osfunc.c:85:2: error: #error "A preemptible Linux kernel is required when using workqueues" That sounds very very wrong :).

Here is the code: #if defined(PVR_LINUX_USING_WORKQUEUES) && !defined(CONFIG_PREEMPT) /* * Services spins at certain points waiting for events (e.g. swap * chain destrucion). If those events rely on workqueues running, * it needs to be possible to preempt the waiting thread. * Removing the need for CONFIG_PREEMPT will require adding preemption * points at various points in Services. */ #error "A preemptible Linux kernel is required when using workqueues" #endif So, could we remove those lines safely?

...

...
...
...
Is there any objection to move to a preemptible kernel for omap2plus? For other ARM boards? For Factory and/or 12.2? It usually incurs overhead for not too much perceivable gain. Have you run into latency issues? No, but it may be useful for people using sound or things like that which need low latency. Well, we can switch _all_ our kernels to PREEMPT_VOLUNTARY.

According to the code, it is CONFIG_PREEMPT which is needed. Maybe we could ignore it or use PREEMT_VOLONTARY, safely? Guillaume

...

Alex

-- To unsubscribe, e-mail: opensuse-arm+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-arm+owner@opensuse.org

Alexander Graf

14:00

On 12.10.2012, at 11:36, Guillaume Gardet wrote:

...

Le 11/10/2012 22:14, Alexander Graf a écrit :

...
On 11.10.2012, at 18:46, guillaume.gardet@free.fr wrote:

...
----- Alexander Graf a écrit :

...
On 11.10.2012, at 17:45, Guillaume Gardet wrote:

...
Hi,

Does anybody thought about kernel preemption for ARM boards? It could be usefull since kernel preemption is intended to embedded system or (Low-latency) Desktop.

Moreover, If we want to enable openGL on omap4 (pandaboard), we need a preemptible kernel. Why? It is a build requirement, otherwise, we get: [ 664s] /home/abuild/rpmbuild/BUILD/pvr-omap4-kernel-1330667111/sgx/eurasiacon/binary2_omap4430_linux_release/target/kbuild/services4/srvkm/env/linux/osfunc.c:85:2: error: #error "A preemptible Linux kernel is required when using workqueues" That sounds very very wrong :).

Here is the code: #if defined(PVR_LINUX_USING_WORKQUEUES) && !defined(CONFIG_PREEMPT) /* * Services spins at certain points waiting for events (e.g. swap * chain destrucion). If those events rely on workqueues running, * it needs to be possible to preempt the waiting thread. * Removing the need for CONFIG_PREEMPT will require adding preemption * points at various points in Services. */ #error "A preemptible Linux kernel is required when using workqueues" #endif

So, could we remove those lines safely?

Sigh. Sounds like broken sgx code to me. No, let's just enable preempt for the omap kernel. And consider me not surprised. Apparently the sgx code quality is even worse than I heard already. Should I do the config patch or do you want to assemble a patch against the 12.2 and master branches? Alex

...

...
...
...
...
Is there any objection to move to a preemptible kernel for omap2plus? For other ARM boards? For Factory and/or 12.2? It usually incurs overhead for not too much perceivable gain. Have you run into latency issues? No, but it may be useful for people using sound or things like that which need low latency. Well, we can switch _all_ our kernels to PREEMPT_VOLUNTARY.

According to the code, it is CONFIG_PREEMPT which is needed. Maybe we could ignore it or use PREEMT_VOLONTARY, safely?

Guillaume

...
Alex

-- To unsubscribe, e-mail: opensuse-arm+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-arm+owner@opensuse.org

4223

Age (days ago)

4224

Last active (days ago)

List overview

Download

8 comments

4 participants

participants (4)

Alexander Graf
Andrew Wafaa
Guillaume Gardet
guillaume.gardet＠free.fr