Messages in this thread | | | Date | Sun, 8 Jul 2007 20:53:28 -0700 (PDT) | From | Fernando Pablo Lopez-Lezcano <> | Subject | Re: v2.6.21.5-rt19 |
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On Mon, 9 Jul 2007, Gabriel C wrote: > 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. >>> >> 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.
More tests...
The problem is the rt kernel AFAICT, this goes beyond Flash 9, way beyond:
_OpenOffice_ hangs with 2.6.21.5-rt20, works fine with stock Fedora 7 kernel. Flash 9 hangs with 2.6.21.5-rt20, works fine with the stock Fedora 7 kernel. Same machine booting different kernels, I'd say it is the kernel.
The only way out for a hung app is a reboot.
Ingo: what would be a good way to trace this? It makes the rt kernels not very usable at least on this hardware (more tests tomorrow in the CCRMA machines).
Same on 2.6.21.5-rt18 with CONFIG_NO_HZ not set.
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