linux-kernel - Re: [PATCH 0/2] Boottime: measure bootloader and kernel bootup time

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Message-ID: <20121115105752.GC4398@game.jcrosoft.org>
Date:	Thu, 15 Nov 2012 11:57:52 +0100
From:	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>
To:	Lee Jones <lee.jones@...aro.org>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	will.deacon@....com, jonas.aberg@...ricsson.com,
	linux@....linux.org.uk, linus.walleij@...ricsson.com, arnd@...db.de
Subject: Re: [PATCH 0/2] Boottime: measure bootloader and kernel bootup time

On 10:35 Thu 15 Nov     , Lee Jones wrote:
> On Thu, 15 Nov 2012, Jean-Christophe PLAGNIOL-VILLARD wrote:
> 
> > On 10:04 Thu 15 Nov     , Lee Jones wrote:
> > > This patchset supplies a new tool which measures boottime inclusive
> > > of bootloader involvement. It seems to be accurate and adds no
> > > latency to the booting of the system.
> > > 
> > > In the first round of testing we booted the kernel 3 times each with
> > > boottime enabled and disabled. Actually, when it was disabled, the
> > > code was completely removed from the kernel source and the kernel was
> > > rebuilt. The difference between present & enabled and completely
> > > removed was very little indeed. In fact, averaging out the 3 runs of
> > > each, when boottime was enabled the system booted 4ms _faster_, go
> > > figure!
> > > 
> > >              Enabled    Disabled
> > >   1st run    2.983093   2.985168
> > >   2nd run    2.973266   2.971801
> > >   3rd run    2.975402   2.987304
> > >   Average    2.977254   2.981424   -0.004171 (-4ms)
> > > 
> > > 
> > > For the next round of testing, we delayed the bootloader for varying
> > > amounts of time, then started to remove key components from kernel
> > > functionality to see if the boottime system would pick-up on them.
> > > 
> > >   /* Hang around in the bootloader for a while. */
> > >   $ cat /sys/kernel/debug/boottime/summary 
> > >     kernel: 42864 msecs
> > >     total: 42864 msecs
> > >     kernel: cpu0 system: 56% idle: 43% iowait: 0% irq: 0% 
> > >             cpu1 system: 4% idle: 95% iowait: 0% irq: 0%
> > > 
> > >   /* Hang around in the bootloader for a smaller amount of time. */
> > >     kernel: 12351 msecs
> > >     total: 12351 msecs
> > >     kernel: cpu0 system: 56% idle: 43% iowait: 0% irq: 0% 
> > >             cpu1 system: 2% idle: 97% iowait: 0% irq: 0%
> > >   
> > >   /* Instant boot. (1st run) */
> > >     kernel: 7833 msecs
> > >     total: 7833 msecs
> > >     kernel: cpu0 system: 55% idle: 44% iowait: 0% irq: 0% 
> > >             cpu1 system: 3% idle: 96% iowait: 0% irq: 0%
> > > 
> > >   /* Instant boot. (2nd run) */
> > >     kernel: 7817 msecs
> > >     total: 7817 msecs
> > >     kernel: cpu0 system: 53% idle: 46% iowait: 0% irq: 0% 
> > >             cpu1 system: 8% idle: 91% iowait: 0% irq: 0%
> > > 
> > >   /* Instant boot. (3rd run) */
> > >     kernel: 7747 msecs
> > >     total: 7747 msecs
> > >     kernel: cpu0 system: 56% idle: 42% iowait: 0% irq: 0% 
> > >             cpu1 system: 2% idle: 97% iowait: 0% irq: 0%
> > 7/8s? on a u9500 wow it's really slow
> 
> No, this is a u8500.
> 
> > I do 2/3s here
> 
> Really? You installed this quick.
> 
> Are you sure you did it correctly?
yes we spend less than 2s (~ 1.5s) in the bootloader

I measure it via scope
> 
> Don't forget, this times from power-on to userspace.
yes

to the shell prompt

and gexbox 13s IIRC application

Best Regards,
J.
> 
> -- 
> Lee Jones
> Linaro ST-Ericsson Landing Team Lead
> Linaro.org │ Open source software for ARM SoCs
> Follow Linaro: Facebook | Twitter | Blog
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