Messages in this thread | | | Date | Thu, 14 Jun 2018 11:08:04 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [RFC 1/2] printk: Enable platform to provide a early boot clock |
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On Thu, 14 Jun 2018, Feng Tang wrote: > On Wed, May 30, 2018 at 05:20:58PM +0800, Feng Tang wrote: > > Currently printk timestamp mostly come from the sched_clock which > > depends on the clock setup, so there are many kernel logs started > > with "[ 0.000000] " before the clock is calibrated. > > > > This patch will provide an debug option for specific platform to > > provide a early boot time clock, so that we can have time info in > > kernel log much earlier, which can show the time info for the early > > kernel boot, and make boottime tuning/optimization easier (boot time > > is critical for phone/tablet and embedded devices). > > > > Capable platform only need to setup the "boot_printk_clock_fn" > > which could return time in nano seconds. > > > > Together with a TSC patch on x86 system, we have easily captured > > some early boottime killer like unwind_init() which takes about > > 300ms in boot phase. > > Hi Petr and all, > > As the 2/2 tsc related patch is still under review/discussion, can > we consider taking this first? As this may benefit other archs. > For example, Intel Curie platform has an always-on 32KHz osc clock, > which is accurate but low frequency, and it could be used as > early printk timestamp until the high-resolution timer is initialized > and used as sched_clock. Don't know if ARM or other platforms > have similar use case.
Can we please _NOT_ add half sorted core stuff in a hurry?
Thanks,
tglx
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