Messages in this thread | | | From | Pavel Tatashin <> | Subject | [v2 0/9] Early boot time stamps for x86 | Date | Fri, 24 Mar 2017 11:21:30 -0400 |
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changelog --------- v1 - v2 In patch "x86/tsc: tsc early": - added tsc_adjusted_early() - fixed 32-bit compile error use do_div()
Adding early boot time stamps support for x86 machines. SPARC patch see here: http://www.spinics.net/lists/sparclinux/msg17372.html
sample output ------------- Before: https://hastebin.com/zofiqazuze.scala
After: https://hastebin.com/otayoliruc.scala
example why early time is crucial --------------------------------- Here is boot log on x86 machine with 8 E7-8895 CPUs, and 1T of memory: https://hastebin.com/ebidosafic.pas
We want to improve boot time, by deferring vmemmap initialization to when the secondary CPUs are online: https://hastebin.com/migajadiju.pas
We see in the log that struct pages are initialized in parallel: [ 19.446609] node 0 initialised, 31980145 pages in 530ms ...
But, we have no idea if we saved overall boot time or not by enabling this feature, because the total boot time as shown currently has not changed much, and is actually increased from: 18.99s to 19.52s
Now, with this feature we would see right away that the time is actually decreased: Before: https://hastebin.com/ivobehahud.pas After: https://hastebin.com/uvifasohon.pas
Boot time reduced from 40.68s to 31.41s, we saved 30% by enabling deferred page initialization feature, great.
However, now, we have early boot time stamps, and we can analyze even further, and see that we still spend a lot of time in this interval: [ 0.009071] kexec_core: crashkernel: memory value expected [ 11.255710] Zone ranges:
And, this is where this fix comes handy: https://lkml.org/lkml/2017/3/23/864
The final boot time on this machine is this: https://hastebin.com/anodiqaguj.pas
So, 20.7 seconds vs. 40.68s before, and we can show it with the early boot time stamps, and avoid future regressions by having this data always available to us.
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 | 186 ++++++++++++++++++++++++++++++++++----- arch/x86/kernel/tsc_msr.c | 38 +++++--- include/linux/sched/clock.h | 4 + kernel/sched/clock.c | 70 ++++++++++++++- 9 files changed, 304 insertions(+), 38 deletions(-)
-- 1.8.3.1
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