On Tue, 11 Dec 2007 00:34:33 +0100 Stefano Brivio <[EMAIL PROTECTED]> wrote:
> On Tue, 11 Dec 2007 00:04:25 +0100 > Ingo Molnar <[EMAIL PROTECTED]> wrote: > > > > * Ingo Molnar <[EMAIL PROTECTED]> wrote: > > > > > * Andrew Morton <[EMAIL PROTECTED]> wrote: > > > > > > > > what do you think? Right now i've got them queued up for > > > > > 2.6.25 in both the scheduler-devel and the x86-devel git > > > > > trees - but can submit them for 2.6.24 if it's better if we > > > > > did them there. I've got no strong opinion either way. > > > > > > > > printk_clock() doesn't seem terribly important but what's this > > > > stuff about effects on udelay/mdelay? That can be serious if > > > > they're getting shortened. > > > > > > since udelay depends on loops_per_jiffy, which is fixed up > > > time_cpufreq_notifier(), i dont see how it could be affected by > > > frequency changes. (but that's the theory - practice might be > > > different) > > > > Stefano Brivio reported udelay()/mdelay() effects in the b43 > > driver. (and it caused driver failures for him.) > > > > Stefano, could you please try to sum up your experiences with that > > issue? Is it reproducable, and the 5 patches i did fix it? (if yes, > > could you try to re-do the mdelay verifications perhaps, to make > > sure it's not some other effect interacting here. In theory > > sched-clock scaling has no effect on udelay behavior.) > > Sorry for disappearing. Anyway, yes, those patches fixed it. > Precision in delays isn't that good when using my crappy unstable TSC > (mdelay(2000) causes delays between 2 and 2.9 seconds) but it's not > depending on frequency changes anymore. So I'd say it's fixed, but > please tell me if you want me to do any other test so as to be sure > it is. > > I'm still quite concerned about this in dual/quad core scenarios; the frequency of both cores is the maximum of what linux sets each core to; this means that if you're THIS sensitive to that there still is quite a nasty issue there. I wonder if the various delay functions (maybe only in .25) should use the maximum observed loops_per_jiffie instead always (across cpus) to be super safe here. -- If you want to reach me at my work email, use [EMAIL PROTECTED] For development, discussion and tips for power savings, visit http://www.lesswatts.org -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
