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Old 05-13-2008, 01:40 PM
"Alessio Igor Bogani"
 
Default SRU Bug #229499

Hi Kernel Team,

SRU Justification:

Bug Description: Recently i have worked on just upgraded Hardy
systems.I have noticed that there is a don't clearly visible
regression about rt kernel flavour. It seems that on 2.6.24 the
Dynamic Ticks features is incompatible with CONFIG_PREEMPT_RT. This
cause huge latency and it is a regression respect Gutsy!

Impact: That bug affect all rt kernel flavour users. From a realtime
point of view this is a severe regression.

Fix Description: To prevent this latency we need to disable Dynamic Ticks.

Patch is very simple and safe (one line in rt kernel configuration):
http://kernel.ubuntu.com/git?p=abogani/ubuntu-hardy-rt.git;a=commit;h=f80aed2d95a5be145a31b80d30fad866 72b16e8c

Drawback: A bit more power consumption.

TEST CASE: I was able to put problem clearly visible using cyclictest,
a realtime kernel test utility, on a couple of systems.
[Dynamic Ticks on]
abogani@picasso:~/WIP/rt-tests$ sudo ./cyclictest -t1 -n -p99 -q -l200000
T: 0 ( 7140) P:99 I:1000 C: 200000 Min: 4 Act: 40 Avg: 65 Max: 12047

[Dynamic Ticks off]
abogani@picasso:~/WIP/rt-tests$ sudo ./cyclictest -t1 -n -p99 -q -l200000
T: 0 ( 6481) P:99 I:1000 C: 200000 Min: 2 Act: 6 Avg: 6 Max: 321

For this reason please pull:
The following changes since commit 45a2f1fa59db5a20f63cd3f120cf5df5f51d0e0b:
Tim Gardner (1):
UBUNTU: V4L/DVB (7132): Add USB ID for a newer variant of
Hauppauge WinTV-HVR 900

are available in the git repository at:

git://kernel.ubuntu.com/abogani/ubuntu-hardy-rt.git master

Alessio Igor Bogani (1):
UBUNTU: rt: Disable Dynamic Ticks (CONFIG_NO_HZ)

debian/binary-custom.d/rt/config.amd64 | 7 ++-----
debian/binary-custom.d/rt/config.i386 | 7 ++-----
2 files changed, 4 insertions(+), 10 deletions(-

Thanks!

Ciao,
Alessio

--
kernel-team mailing list
kernel-team@lists.ubuntu.com
https://lists.ubuntu.com/mailman/listinfo/kernel-team
 
Old 05-13-2008, 03:40 PM
Tim Gardner
 
Default SRU Bug #229499

Alessio Igor Bogani wrote:
> Hi Kernel Team,
>
> SRU Justification:
>
> Bug Description: Recently i have worked on just upgraded Hardy
> systems.I have noticed that there is a don't clearly visible
> regression about rt kernel flavour. It seems that on 2.6.24 the
> Dynamic Ticks features is incompatible with CONFIG_PREEMPT_RT. This
> cause huge latency and it is a regression respect Gutsy!
>
> Impact: That bug affect all rt kernel flavour users. From a realtime
> point of view this is a severe regression.
>
> Fix Description: To prevent this latency we need to disable Dynamic Ticks.
>
> Patch is very simple and safe (one line in rt kernel configuration):
> http://kernel.ubuntu.com/git?p=abogani/ubuntu-hardy-rt.git;a=commit;h=f80aed2d95a5be145a31b80d30fad866 72b16e8c
>
> Drawback: A bit more power consumption.
>
> TEST CASE: I was able to put problem clearly visible using cyclictest,
> a realtime kernel test utility, on a couple of systems.
> [Dynamic Ticks on]
> abogani@picasso:~/WIP/rt-tests$ sudo ./cyclictest -t1 -n -p99 -q -l200000
> T: 0 ( 7140) P:99 I:1000 C: 200000 Min: 4 Act: 40 Avg: 65 Max: 12047
>
> [Dynamic Ticks off]
> abogani@picasso:~/WIP/rt-tests$ sudo ./cyclictest -t1 -n -p99 -q -l200000
> T: 0 ( 6481) P:99 I:1000 C: 200000 Min: 2 Act: 6 Avg: 6 Max: 321
>
> For this reason please pull:
> The following changes since commit 45a2f1fa59db5a20f63cd3f120cf5df5f51d0e0b:
> Tim Gardner (1):
> UBUNTU: V4L/DVB (7132): Add USB ID for a newer variant of
> Hauppauge WinTV-HVR 900
>
> are available in the git repository at:
>
> git://kernel.ubuntu.com/abogani/ubuntu-hardy-rt.git master
>
> Alessio Igor Bogani (1):
> UBUNTU: rt: Disable Dynamic Ticks (CONFIG_NO_HZ)
>
> debian/binary-custom.d/rt/config.amd64 | 7 ++-----
> debian/binary-custom.d/rt/config.i386 | 7 ++-----
> 2 files changed, 4 insertions(+), 10 deletions(-
>
> Thanks!
>
> Ciao,
> Alessio
>

I noticed while looking at the diff that there are more changes then
just CONFIG_NO_HZ. Was this intentional? I thought
CONFIG_FAIR_CGROUP_SCHED=y was the preferred setting.

rtg
--
Tim Gardner tim.gardner@ubuntu.com

--
kernel-team mailing list
kernel-team@lists.ubuntu.com
https://lists.ubuntu.com/mailman/listinfo/kernel-team
 
Old 05-13-2008, 07:07 PM
Tim Gardner
 
Default SRU Bug #229499

Tim Gardner wrote:
> Alessio Igor Bogani wrote:
>> Hi Kernel Team,
>>
>> SRU Justification:
>>
>> Bug Description: Recently i have worked on just upgraded Hardy
>> systems.I have noticed that there is a don't clearly visible
>> regression about rt kernel flavour. It seems that on 2.6.24 the
>> Dynamic Ticks features is incompatible with CONFIG_PREEMPT_RT. This
>> cause huge latency and it is a regression respect Gutsy!
>>
>> Impact: That bug affect all rt kernel flavour users. From a realtime
>> point of view this is a severe regression.
>>
>> Fix Description: To prevent this latency we need to disable Dynamic Ticks.
>>
>> Patch is very simple and safe (one line in rt kernel configuration):
>> http://kernel.ubuntu.com/git?p=abogani/ubuntu-hardy-rt.git;a=commit;h=f80aed2d95a5be145a31b80d30fad866 72b16e8c
>>
>> Drawback: A bit more power consumption.
>>
>> TEST CASE: I was able to put problem clearly visible using cyclictest,
>> a realtime kernel test utility, on a couple of systems.
>> [Dynamic Ticks on]
>> abogani@picasso:~/WIP/rt-tests$ sudo ./cyclictest -t1 -n -p99 -q -l200000
>> T: 0 ( 7140) P:99 I:1000 C: 200000 Min: 4 Act: 40 Avg: 65 Max: 12047
>>
>> [Dynamic Ticks off]
>> abogani@picasso:~/WIP/rt-tests$ sudo ./cyclictest -t1 -n -p99 -q -l200000
>> T: 0 ( 6481) P:99 I:1000 C: 200000 Min: 2 Act: 6 Avg: 6 Max: 321
>>
>> For this reason please pull:
>> The following changes since commit 45a2f1fa59db5a20f63cd3f120cf5df5f51d0e0b:
>> Tim Gardner (1):
>> UBUNTU: V4L/DVB (7132): Add USB ID for a newer variant of
>> Hauppauge WinTV-HVR 900
>>
>> are available in the git repository at:
>>
>> git://kernel.ubuntu.com/abogani/ubuntu-hardy-rt.git master
>>
>> Alessio Igor Bogani (1):
>> UBUNTU: rt: Disable Dynamic Ticks (CONFIG_NO_HZ)
>>
>> debian/binary-custom.d/rt/config.amd64 | 7 ++-----
>> debian/binary-custom.d/rt/config.i386 | 7 ++-----
>> 2 files changed, 4 insertions(+), 10 deletions(-
>>
>> Thanks!
>>
>> Ciao,
>> Alessio
>>
>
> I noticed while looking at the diff that there are more changes then
> just CONFIG_NO_HZ. Was this intentional? I thought
> CONFIG_FAIR_CGROUP_SCHED=y was the preferred setting.
>
> rtg

Pulled. Ignore previous comment, I confused it with CONFIG_CGROUPS=y.

--
Tim Gardner tim.gardner@ubuntu.com

--
kernel-team mailing list
kernel-team@lists.ubuntu.com
https://lists.ubuntu.com/mailman/listinfo/kernel-team
 

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