linux-kernel - Re: [PATCH RFC] USB: Add HCD fastboot

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Date:	Fri, 08 Aug 2008 11:24:21 +0200
From:	Rene Herman <rene.herman@...access.nl>
To:	Simon Arlott <simon@...e.lp0.eu>
CC:	Alan Stern <stern@...land.harvard.edu>,
	Arjan van de Ven <arjan@...radead.org>,
	linux-kernel@...r.kernel.org, mingo@...e.hu,
	Daniel Walker <dwalker@...sta.com>,
	USB list <linux-usb@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...e.de>
Subject: Re: [PATCH RFC] USB: Add HCD fastboot

On 06-08-08 20:40, Simon Arlott wrote:

>>> Ok - so there could be some big improvements to be had by making the 
>>> hcd init happen as early as possible and the device initcalls later?
>>
>> Maybe.  Perhaps a better approach would be to make the device driver 
>> initcalls before there are any devices for their probe routines to 
>> block on.
> 
> What about this?
> 
> The Makefiles become a bit messy, but by moving things around I get the 
> desired effect without splitting their initcalls.
> 
> [    7.941890] Write protecting the kernel read-only data: 5656k
> [    5.437709] Write protecting the kernel read-only data: 5656k
> 
> 2.5s faster, which is almost half the boot time.
> 
> Signed-off-by: Simon Arlott <simon@...e.lp0.eu>

Interesting... I haven't been able to get stable improvements, with all 
USB kernel modules built-in, just a USB mouse on OHCI and otherwise a 
switched of USB HD on EHCI and usb-storage, but I do get the idea that 
with your parch, I "get lucky" more often.

I have knfsd as a module and it loads through the exportfs trigger 
during bootup and outputs the last message to my dmesg:

4 boots without your patch: 6.12, 6.41, 6.38, 6.34 seconds
4 boots with              : 5.39, 6.33, 5.37, 6.34

Booting with the external HD switched on adds a tiny bit to the actual 
kernel startup time -- completely repeatable 2.62 seconds until freeing 
init code with the HD off versus 2.73 with it on -- but doesn't seem to 
change the picture otherwise...

Would those results make sense you feel? I'm not looking forward to 
putting an actual statistical analysis on it ;-)

Arjan: your fastboot repo by the way doesn't pull cleanly into current 
upstream anymore.

Rene.
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