Hello, On Fri, 30 Nov 2007 00:26:47 +0300 Michael Tokarev <[EMAIL PROTECTED]> wrote:
> H. Peter Anvin wrote: > > Paul Rolland (ポール・ロラン) wrote: > [] > >> Measured 3978592228 cycles TSC warp between CPUs, turning off TSC clock. > >> Marking TSC unstable due to: check_tsc_sync_source failed. > [] > >> but I was wondering if this is a bug or a feature ;) > > > The problem you're having is that the TSCs of your two cores are > > completely different, over a second apart. This is a bug, unrelated to > > constant_tsc. > > A bug in where - in the CPU or in kernel? Good question ! > The thing is that all our dual-core machines shows something like > that. > > (not that huge difference as Paul reported, but still "unstable". > The same happens with 2.6.23) I've been checking my logs, and the difference is quite constant and huge : [EMAIL PROTECTED] log]# grep 'cycles TSC warp' messages* messages:Nov 26 08:27:56 tux kernel: Measured 4078687691 cycles TSC warp between C PUs, turning off TSC clock. messages:Nov 26 17:21:21 tux kernel: Measured 3978592228 cycles TSC warp between C PUs, turning off TSC clock. messages.1:Nov 18 22:52:23 tux kernel: Measured 4063102940 cycles TSC warp between CPUs, turning off TSC clock. messages.1:Nov 19 07:19:02 tux kernel: Measured 4057192061 cycles TSC warp between CPUs, turning off TSC clock. messages.1:Nov 23 20:50:12 tux kernel: Measured 4064589321 cycles TSC warp between CPUs, turning off TSC clock. messages.2:Nov 12 08:06:44 tux kernel: Measured 4072130361 cycles TSC warp between CPUs, turning off TSC clock. messages.2:Nov 13 19:42:47 tux kernel: Measured 4049899451 cycles TSC warp between CPUs, turning off TSC clock. messages.2:Nov 17 09:27:22 tux kernel: Measured 4066629060 cycles TSC warp between CPUs, turning off TSC clock. messages.3:Nov 5 08:25:08 tux kernel: Measured 4086386109 cycles TSC warp between CPUs, turning off TSC clock. messages.3:Nov 8 13:07:08 tux kernel: Measured 4041945934 cycles TSC warp between CPUs, turning off TSC clock. messages.3:Nov 9 23:31:24 tux kernel: Measured 4092303059 cycles TSC warp between CPUs, turning off TSC clock. messages.4:Oct 29 07:28:23 tux kernel: Measured 4096946373 cycles TSC warp between CPUs, turning off TSC clock. messages.4:Oct 31 17:07:21 tux kernel: Measured 4046765372 cycles TSC warp between CPUs, turning off TSC clock. messages.4:Oct 31 17:15:09 tux kernel: Measured 4039328228 cycles TSC warp between CPUs, turning off TSC clock. messages.4:Oct 31 23:19:00 tux kernel: Measured 4069714246 cycles TSC warp between CPUs, turning off TSC clock. messages.4:Nov 1 20:33:02 tux kernel: Measured 4088199726 cycles TSC warp between CPUs, turning off TSC clock. messages.4:Nov 2 11:53:17 tux kernel: Measured 4079927527 cycles TSC warp between CPUs, turning off TSC clock. messages.4:Nov 3 09:37:16 tux kernel: Measured 4071112656 cycles TSC warp between CPUs, turning off TSC clock. messages.4:Nov 3 10:51:29 tux kernel: Measured 3986266219 cycles TSC warp between CPUs, turning off TSC clock. messages.4:Nov 4 18:14:56 tux kernel: Measured 4074214144 cycles TSC warp between CPUs, turning off TSC clock. > Note that once TSC is disabled (it's using "jiffies" as far > as I can see), ntpd constantly speeds up and slows down the > clock, it jumps +/- 0.5sec every several minutes or hours - > I guess that's when ntpd process gets moved from one core > to another for whatever reason. And an interesting thing > is that with 64bits kernel this TSC problem does not occur > on this very machine. Hmmmm.... That could make it a problem related to kernel rather than CPU. > Something similar is reported on AMD X2 64 machines as well -- > can't check right now. If I recall correctly, issues with AMD X2 where related to TSC being independant for each core and not constant (speed depending of C state). But the reason I raise the issue is that the Core2 reports constant TSC, so there is (IMHO) no reason for that. Paul - 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/