Re: v2.6.21.5-rt19

[Gabriel C <nix.or.die@googlemail.com>]

Fernando Lopez-Lezcano wrote:
> On Sat, 2007-07-07 at 11:24 +0200, Ingo Molnar wrote:
>   
>> * Fernando Lopez-Lezcano <nando@ccrma.Stanford.EDU> wrote:
>>     
>>>>> Changes since 2.6.21.5-rt18:
>>>>>
>>>>> - Fixed a nasty and hard to track down slowness / boot problem on SMP
>>>>> machines with CONFIG_NOHZ enabled. The problem was caused by the timer
>>>>> wheel base lock held during the get_next_timer_interrupt() call in the
>>>>> idle path, which eventually led to a bogus PI boosting of the idle task
>>>>> and in consequence a stale wrong scheduler selection for the affected idle
>>>>> task.
>>>>>
>>>>> Kudos to Carsten Emde, who patiently and meticulously isolated the
>>>>> problem and provided the traces, which allowed to identify the root cause.
>>>>>
>>>>> Problem solution: Prevent idle task boosting
>>>>>           
>>>> Maybe someone remember me whining about troubles with 2.6.21-rt2..18 
>>>> on my Core2 T7200 laptop (fujitsu-siemens amilo i1520).
>>>>
>>>> Althought I'm still with my fingers crossed, I can tell the good 
>>>> news are that 2.6.21.5-rt19 (and -rt20) does behave far better now 
>>>> on the very same box.
>>>>         
>>> Yes, it works much better indeed...
>>>
>>> Ingo: is there a place where I can read about the changes in different 
>>> rtxx releases? What is new/better/fixed in rt20? (I see scheduler 
>>> stuff in a diff from rt19 to rt20 but I don't really know what it 
>>> means).
>>>       
>> and rt18 was a -rt-only NOHZ fix, that bug got introduced in rt11 when 
>> CFS was merged.
>>
>> i _think_ Rui might have seen two separate problems. Perhaps by the time 
>> we fixed the first problem (which Rui saw since -rt2) we introduced the 
>> other one via -rt11 - which then got fixed in -rt19.
>>     
>
> Ahh, CFS is now part of rt, I was obviously not paying attention... I'm
> really trying to provide a "stable" rt kernel for audio usage and
> including another subsystem into rt is - IMHO - not going to help.
> What's the chance of splitting things?
>
>   
>> btw., we'd love to get more feedback regarding CFS. CFS is a completely 
>> new scheduler for Linux. 
>>     
>
> Then I'd rather have it separate from rt. 
>
>   
>> It has a design centered around keeping 
>> application latencies down, so it is ultimately real-time friendly, and 
>> it should also make things work better for desktop-ish and audio-ish 
>> stuff as well. (even under SCHED_OTHER)
>>     
>
> Maybe this is CFS related? (tail of a thread in the Planet CCRMA mailing
> list):
>
> On Sun, 2007-07-08 at 15:26 -0400, Hector Centeno wrote:
>   
>> Ok, so just to confirm, that 2.6.21-0182.rt19.1.fc7.ccrmart works fine
>> on my desktop but on my laptop it makes Firefox and Tomboy to crash.
>> On the same laptop using 2.6.21-0182.rt17.1.fc7.ccrmart there is no
>> problem.
>>
>> Cheers,
>>
>> Hector
>>
>>
>> On 7/7/07, Hector Centeno <hcengar@gmail.com> wrote:
>>         Hi Fernando,
>>         
>>         I do have Flash installed but for me Firefox crashes when
>>         trying to
>>         access gmail (which AFAIK doesn't use Flash, does it?). Right
>>         now
>>         Firefox is frozen and I'm typing this email using Konkeror (in
>>         Gnome). 
>>         This is ps' output:
>>         
>>         hector    3595  1.1  2.2 194352 46336 ?        D    16:25
>>         0:03
>>         /usr/lib/firefox-2.0.0.4/firefox-bin
>>         
>>         I think the problem is not present in my Desktop but I have to
>>         double 
>>         check. In the same laptop using the stock fedora kernel both
>>         Tomboy
>>         and Firefox work fine. My laptop has a centrino duo processor,
>>         2 gigs
>>         of ram and the Inte GMA950 graphics chip.
>>         
>>         Hector
>>     
>
> I managed to completely hang firefox (fc7) with flash 9 installed
> (unkillable even with -9).

Firefox with flash 9 does not work good , there are a lot bugs reported 
about ( just google ) and it hangs on vanilla or
whatever other kernels as well. Not only Firefox but also  Swiftfox, 
Opera, Epiphany etc.

The most time Firefox dies when you use flash 9 and close a window or a tab.

>  Does not seem to happen with flash 7.

Yes flash 7 is fine.

>  Have
> not tried yet with gmail and flash uninstalled. I'll try to strace it to
> see when/why it hangs. 
>
>   
> -- Fernando
>
>
>   
>> So it would be nice if you could keep an extra eye on any scheduling 
>> artifacts or regressions, and make sure your favorite workload is still 
>> handled by the Linux scheduler in the utmost best way. I'd like to hear 
>> about any sort of "scheduling behavior / interactivity" regression you 
>> might see, relative to the vanilla kernel. Or if you can see no such 
>> problems then a line of "it works as well as the previous scheduler" is 
>> important info to us too. Thanks!
>>     
>
>
>   


Regards,

Gabriel C