|From:||Thomas Gleixner <tglx-AT-linutronix.de>|
|To:||Andi Kleen <ak-AT-suse.de>|
|Subject:||Re: [patch 13/19] GTOD: Mark TSC unusable for highres timers|
|Date:||Sat, 11 Nov 2006 12:14:37 +0100|
|Cc:||Andrew Morton <akpm-AT-osdl.org>, Ingo Molnar <mingo-AT-elte.hu>, john stultz <johnstul-AT-us.ibm.com>, LKML <linux-kernel-AT-vger.kernel.org>, Len Brown <lenb-AT-kernel.org>, Arjan van de Ven <arjan-AT-infradead.org>, Roman Zippel <zippel-AT-linux-m68k.org>|
On Fri, 2006-11-10 at 10:29 +0100, Andi Kleen wrote: > > But that's different. > > > > We're limping along in a semi-OK fashion with the TSC. But now Thomas is > > proposing that we effectively kill it off for all x86 because of hrtimers. > > I'm totally against that. I'm working on that. The general disable is indeed overkill. All I need to prevent is to switch over to highres/dyntick in case that there is no fallback (e.g. pm_timer) available. Else I end up in a circular dependency as the emulated tick depends on the monotonic clock. > > And afaict the reason for that is that we're using jiffies to determine if > > the TSC has gone bad, and that test is getting false positives. > > The i386 clocksource had always trouble with that. e.g. I have a box > where the TSC works perfectly fine on a 64bit kernel, but since the new i386 > clocksource code is in it always insists on disabling it shortly after boot. > My guess is that some of the checks in there are just broken and need > to be fixed. It's the unconditional mark_unstable call in ACPI C2 state. /me looks. tglx
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