Date: Thu, 15 Nov 2012 11:15:08 +0100
From: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
To: Lee Jones <lee.jones@linaro.org>
Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        will.deacon@arm.com, jonas.aberg@stericsson.com,
        linux@arm.linux.org.uk, linus.walleij@stericsson.com, arnd@arndb.de
Subject: Re: [PATCH 0/2] Boottime: measure bootloader and kernel bootup time
Message-ID: <20121115101508.GB4398@game.jcrosoft.org>
References: <1352973847-21605-1-git-send-email-lee.jones@linaro.org>
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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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