Messages in this thread | | | Date | Fri, 6 Jun 2008 11:25:47 -0700 | From | Andrew Morton <> | Subject | Re: strange timestamp in dmesg |
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On Fri, 06 Jun 2008 15:49:26 +0200 Andi Kleen <andi@firstfloor.org> wrote:
> Andrew Morton <akpm@linux-foundation.org> writes: > > >> supports DPO and FUA > >> [ 9.801761] sd 1:0:1:0: [sdc] 143374744 512-byte hardware sectors (73408 MB) > >> [ 9.673388] sd 1:0:1:0: [sdc] Write Protect is off > >> [ 9.673395] sd 1:0:1:0: [sdc] Mode Sense: ab 00 10 08 > >> [ 9.806210] sd 1:0:1:0: [sdc] Write cache: enabled, read cache: enabled, > >> supports DPO and FUA > >> [ 9.806220] sdc: sdc1 > >> [ 9.682136] sd 1:0:1:0: [sdc] Attached SCSI disk > >> [ 13.786405] SGI XFS with large block numbers, no debug enabled > >> [ 13.633457] XFS mounting filesystem sdb2 > >> [ 13.724345] Starting XFS recovery on filesystem: sdb2 (logdev: internal) > >> [ 14.251356] Ending XFS recovery on filesystem: sdb2 (logdev: internal) > >> [ 15.379298] XFS mounting filesystem sdc1 > >> [ 15.468255] Starting XFS recovery on filesystem: sdc1 (logdev: internal) > >> [ 14.514314] Ending XFS recovery on filesystem: sdc1 (logdev: internal) > >> [ 14.767260] warning: `squid' uses 32-bit capabilities (legacy support in use) > >> [ 17.589751] e1000: eth0: e1000_watchdog: NIC Link is Up 1000 Mbps Full > >> Duplex, Flow Control: RX/TX > >> > > > > whoa, that's weird. We've seen timestamps jump forward a single hop of > > ~100000 seconds, but that's all over the place. > > No it's expected since printk uses sched_clock() and sched clock is not synchronous > between CPUs on systems without synchronized/invariant TSC (like Opteron) > All sched_clock() users are expected to handle it.
We've seen a storm of hey-my-timestamps-went-weird reports in just the past month or so. I don't recall it being (such) a problem before that.
Did we change something?
> I always advocated just always using jiffies for printk. The only drawback would > be that it won't increase in interrupt off sections, but if you have > one that is longer than a jiffie then you have enough other problems.
I forget why, but we _were_ going to have an (arch-overrideable) printk_clock() function. And we still could. The x86 implementation of that could fall back to jiffies if the TSCs are out of whack?
<googles>
In fact it looks like we _did_ have a printk_clock(), only someone stole it.
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