linux-kernel - Re: Please revert 5adc55da4a7758021bcc374904b0f8b076508a11 (PCI_MULTITHREAD

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Message-ID: <20070509164207.GA28633@kroah.com>
Date:	Wed, 9 May 2007 09:42:07 -0700
From:	Greg KH <greg@...ah.com>
To:	Cornelia Huck <cornelia.huck@...ibm.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Adrian Bunk <bunk@...sta.de>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: Please revert 5adc55da4a7758021bcc374904b0f8b076508a11
	(PCI_MULTITHREAD_PROBE)

On Wed, May 09, 2007 at 03:38:13PM +0200, Cornelia Huck wrote:
> On Wed, 9 May 2007 02:53:02 -0700,
> Greg KH <greg@...ah.com> wrote:
> 
> > > 2. Sheer volume of devices on a bus. Even if the indivdual probing
> > > doesn't take long, having all devices probed one after the other may
> > > take a lot of time. Putting the actual probe on a thread makes it
> > > possible to run several probes in parallel, thereby cutting probing
> > > time.
> > 
> > Again, not for PCI, right?
> 
> It seems that everyone agrees now that moving PCI over to a new probing
> model without individual driver support was a bad idea. So generic
> multithreaded probing is dead.

Why is it dead?  Since when is PCI the only bus in the system?

> > If you want to implement this for your bus type, fine, I have no
> > objection to that at all, but not for PCI, it's just not worth it.
> 
> Infrastructure for async probing might not be such a bad idea, though.
> (Aren't there some huge PCI-based machines?) However, I don't really
> care whether PCI or SCSI or $HUGE_BUS use it, but serial synchronous
> probing on a bus looks like a killer on most large systems.

PCI probing is just reading stuff from memory.  The slowness happens
when storage devices need to spin up and/or discover attached drives.

So, the async stuff can be done in those buses if wanted/needed, PCI is
not the problem here.

thanks,

greg k-h
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