Messages in this thread | | | Date | Wed, 22 Jan 2014 17:31:22 -0500 | From | Sasha Levin <> | Subject | Re: [PATCH 13/15] sched: Use a static_key for sched_clock_stable |
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On 01/22/2014 12:14 PM, Peter Zijlstra wrote: > On Tue, Jan 21, 2014 at 05:28:37PM -0500, Sasha Levin wrote: >> [ 0.000000] Initmem setup node 30 [mem 0x12ee000000-0x138dffffff] >> [ 0.000000] NODE_DATA [mem 0xcfa42000-0xcfa72fff] >> [ 0.000000] NODE_DATA(30) on node 1 >> [ 0.000000] Initmem setup node 31 [mem 0x138e000000-0x142fffffff] >> [ 0.000000] NODE_DATA [mem 0xcfa11000-0xcfa41fff] >> [ 0.000000] NODE_DATA(31) on node 1 >> [ 0.000000] kvm-clock: Using msrs 4b564d01 and 4b564d00 >> [ 0.000000] kvm-clock: cpu 0, msr 0:cf991001, boot clock >> [133538.294040] Zone ranges: >> [133538.294338] DMA [mem 0x00001000-0x00ffffff] >> [133538.294804] DMA32 [mem 0x01000000-0xffffffff] >> [133538.295223] Normal [mem 0x100000000-0x142fffffff] >> [133538.295670] Movable zone start for each node > > OK, took me a while to fiddle with KVM and all the various muck around > that to reproduce. But I can confirm the below does fix the issue for > me. > > I'm hoping to not have to re-introcude the kevents_up() check, but I > need to figure out what hardware triggered that and test again. > > --- > Subject: sched/clock: Fixup early sched_clock initialization > From: Peter Zijlstra <peterz@infradead.org> > Date: Wed, 22 Jan 2014 12:59:18 +0100 > > The code would assume sched_clock_stable() and switch to !stable > later, this switch brings a discontinuity in time. > > The discontinuity on switching from stable to unstable was always > present, but previously we would set stable/unstable before > initializing TSC and usually stick to the one we start out with. > > So the static_key bits brought an extra switch where there previously > wasn't one. > > Things are further complicated by the fact that we cannot use > static_key as early as we usually call set_sched_clock_stable(). > > Fix things by tracking the stable state in a regular variable and only > set the static_key to the right state on sched_clock_init(), which is > ran right after late_time_init->tsc_init(). > > Before this we would not be using the TSC anyway. > > Fixes: 35af99e646c7 ("sched/clock, x86: Use a static_key for sched_clock_stable") > Cc: jacob.jun.pan@linux.intel.com > Cc: Mike Galbraith <bitbucket@online.de> > Cc: Ingo Molnar <mingo@kernel.org> > Cc: hpa@zytor.com > Cc: paulmck@linux.vnet.ibm.com > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: John Stultz <john.stultz@linaro.org> > Cc: Andy Lutomirski <luto@amacapital.net> > Cc: Arjan van de Ven <arjan@linux.intel.com> > Cc: lenb@kernel.org > Cc: rjw@rjwysocki.net > Cc: Eliezer Tamir <eliezer.tamir@linux.intel.com> > Cc: rui.zhang@intel.com > Reported-by: Sasha Levin <sasha.levin@oracle.com> > Reported-by: dyoung@redhat.com > Signed-off-by: Peter Zijlstra <peterz@infradead.org> > Link: http://lkml.kernel.org/r/20140122115918.GG3694@twins.programming.kicks-ass.net
The patch fixes the problem for me.
Thanks, Sasha
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