On 11/23/2017 07:58 AM, Petr Mladek wrote: > On Wed 2017-11-15 19:15:38, Thomas Gleixner wrote: >> For demonstration purposes only. >> >> Add a disgusting hack to work around the fact that high resolution clock >> MONOTONIC accessors are not available during early boot and return stale >> time stamps accross suspend/resume when the current clocksource is not >> flagged with CLOCK_SOURCE_SUSPEND_ACCESS_OK. >> >> Use local_clock() to provide timestamps in early boot and when the >> clocksource is not accessible after timekeeping_suspend(). In the >> suspend/resume case this might cause non monotonic timestamps. > > I get the non-monotonic times even during boot: > > [ 0.026709] smp: Bringing up secondary CPUs ... > [ 0.027973] x86: Booting SMP configuration: > [ 0.028006] .... node #0, CPUs: #1 > [ 0.004000] kvm-clock: cpu 1, msr 1:3ff51041, secondary cpu clock > ^^^^^^^^ > [ 0.032097] KVM setup async PF for cpu 1 > [ 0.032766] kvm-stealtime: cpu 1, msr 13b00dc40 > [ 0.036502] #2 > [ 0.004000] kvm-clock: cpu 2, msr 1:3ff51081, secondary cpu clock > ^^^^^^^^ > [ 0.040062] KVM setup async PF for cpu 2 > [ 0.040576] kvm-stealtime: cpu 2, msr 13b20dc40 > [ 0.041304] #3 > [ 0.004000] kvm-clock: cpu 3, msr 1:3ff510c1, secondary cpu clock > ^^^^^^^^ > [ 0.048051] KVM setup async PF for cpu 3 > [ 0.048554] kvm-stealtime: cpu 3, msr 13b40dc40 > > > To be honest, I do not feel experienced enough to decide which > solution is acceptable. I would say that only few people care > about timestamps during boot. On the other hand, some tools
It is extremely important to know what happened and how long it took. I agree with Petr, we should figure out a way to guarantee that the timestamp is monotonic. P.
