linux-kernel - [v1 0/9] Early boot time stamps for x86

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Date:   Wed, 22 Mar 2017 16:24:16 -0400
From:   Pavel Tatashin <pasha.tatashin@...cle.com>
To:     x86@...nel.org, linux-kernel@...r.kernel.org, mingo@...hat.com,
        peterz@...radead.org, tglx@...utronix.de, hpa@...or.com
Subject: [v1 0/9] Early boot time stamps for x86

Last week I sent out patches to enable early boot time stamp on SPARC, that
work is now under review:
http://www.spinics.net/lists/sparclinux/msg17372.html

This is continuation for that work, but adding early boot time stamps
support for x86 machines.

Here is example how this information is useful:

Before:
https://hastebin.com/zofiqazuze.scala

After:
https://hastebin.com/otayoliruc.scala

If you take a look at the before case, it seems that this particular x86
machine took only 2 minutes to boot. Which, while can be improved, is not
too bad considering that this machine has 192CPUs and 2.2T of memory.

But, as it can be seen in the fix case,
the time is much longer:
- early boot time stamps account for another 80s!
- early tsc offset is 549s, so it took over 9 minutes to get through POST,
  and GRUB before starting linux

Now, the total boot time is 12m52s, which is really slow.

Pavel Tatashin (9):
  sched/clock: broken stable to unstable transfer
  sched/clock: interface to allow timestamps early in boot
  x86/cpu: determining x86 vendor early
  x86/tsc: early MSR-based CPU/TSC frequency discovery
  x86/tsc: disable early messages from quick_pit_calibrate
  x86/tsc: use cpuid to determine TSC frequency
  x86/tsc: use cpuid to determine CPU frequency
  x86/tsc: tsc early
  x86/tsc: use tsc early

 arch/x86/include/asm/processor.h |    1 +
 arch/x86/include/asm/tsc.h       |    5 +
 arch/x86/kernel/cpu/common.c     |   36 ++++++++
 arch/x86/kernel/head64.c         |    1 +
 arch/x86/kernel/time.c           |    1 +
 arch/x86/kernel/tsc.c            |  166 +++++++++++++++++++++++++++++++++-----
 arch/x86/kernel/tsc_msr.c        |   38 ++++++---
 include/linux/sched/clock.h      |    4 +
 kernel/sched/clock.c             |   70 +++++++++++++++-
 9 files changed, 284 insertions(+), 38 deletions(-)