Date: Sun, 4 Nov 2007 19:58:55 -0800
From: Greg KH <greg@kroah.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephen Hemminger <shemminger@linux-foundation.org>,
       linux-kernel@vger.kernel.org
Subject: Re: device struct bloat
Message-ID: <20071105035855.GA25511@kroah.com>
References: <20071103124823.6059640e@shemminger-laptop> <1194208158.5911.63.camel@lappy>
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On Sun, Nov 04, 2007 at 09:29:18PM +0100, Peter Zijlstra wrote:
> 
> On Sat, 2007-11-03 at 12:48 -0700, Stephen Hemminger wrote:
> > The sizeof(struct device) is way too big, especially in the network device case.
> > We want to support 1000's of device's and the change from class_device to
> > net_device has caused needless bloat.
> > 
> > sizeof(struct device) = 272
> > sizeof(struct class_device) = 92
> >   * not the class_id in class_device could also be removed or changed to
> >      a ptr, since it is redundant for net_devices.
> 
> The thing that surprised me most was that it contains a struct
> semaphore, Greg, is that really needed?

Yes, it serializes bind and unbind stuff for the device.  There are
comments about it in drivers/base/dd.c if you want to look into it.

thanks,

greg k-h
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