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Message-ID: <20121115101508.GB4398@game.jcrosoft.org>
Date: Thu, 15 Nov 2012 11:15:08 +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 10:04 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
I do 2/3s here
Best Regards.
J.
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