[Bugme-new] [Bug 6748] New: Clock drifts by 30% for SMP kernel w/APIC

[bugme-daemon at bugzilla.kernel.org]

http://bugzilla.kernel.org/show_bug.cgi?id=6748

           Summary: Clock drifts by 30% for SMP kernel w/APIC
    Kernel Version: 2.6.17-git5
            Status: NEW
          Severity: high
             Owner: platform_i386 at kernel-bugs.osdl.org
         Submitter: jfrieben at hotmail.com


Most recent kernel where this bug did not occur: n/a
Distribution: Fedora Core Development
Hardware Environment: Dual Pentium II Overdrive on PR440FX 
Software Environment: Fedora Core Development w/SMP enabled kernel
Problem Description: Back in October 2001 (!), I posted a bug report at Red Hat
bugzilla,

  https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=55223 ,

for kernel release 2.4.9 according to which switching on "APIC" made the system
clock run faster. I do not know of any earlier release that might have worked
better, because it was then that I sat up the system. For recent kernels, the
drift is about 30% when the system is idle, thus w/o any network traffic. When
data was transferred over the network, the clock ran forward at up to multiples
of the nominal speed, although for recent kernels this has become less severe.

The issue only occurs for the "SMP" kernel when "APIC" is enabled. Booting the
"UP" kernel or adding "noapic" to the kernel options makes the clock behave
correctly. Consequently, this bug has nothing to with with recent bug reports
about observing clock drift on (single-core) AMD64 systems!

This bug has been roaming for almost 5 years without ever being looked at. I
think it is definitely worth being considered for the hopefully soon to come
kernel maintenance release which has been suggested by A. Morton.

Steps to reproduce:
Install 2.6.17-git5 on PR440FX based system and reboot without adding "noapic"
to the kernel options.

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