linux-kernel - Re: [PATCH 02/39] x86, PCI: have own version for pcibios_bus_to

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Date:	Wed, 29 Feb 2012 18:54:34 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Tony Luck <tony.luck@...el.com>,
	David Miller <davem@...emloft.net>, x86 <x86@...nel.org>,
	Dominik Brodowski <linux@...inikbrodowski.net>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org
Subject: Re: [PATCH 02/39] x86, PCI: have own version for pcibios_bus_to_resource

On Wed, Feb 29, 2012 at 4:42 PM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
> On Wed, Feb 29, 2012 at 4:33 PM, Yinghai Lu <yinghai@...nel.org> wrote:
>> On Wed, Feb 29, 2012 at 3:20 PM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
>>> On Wed, Feb 29, 2012 at 4:07 PM, Yinghai Lu <yinghai@...nel.org> wrote:
>>>> x86 does not need to offset the address. So we can skip that costing offset
>>>> searching.
>>>
>>> I tried to start a discussion about this patch (and others), but I
>>> don't think you responded:
>>> http://marc.info/?l=linux-pci&m=133036414506921&w=2
>>
>> this patch does reduce some not needed ops.
>>
>> and it does not affects your effects,
>
> It does affect my efforts in that this patch adds back x86 complexity
> that I don't think is necessary.
>
> And this patch makes it so the pci_add_resource_offset() interface
> exists and appears to work on x86, but if somebody tries to use it, it
> *doesn't* work.  I don't like to write code like that.  I think it's
> poor style.
>
>> and it just make x86 not get punished.
>
> What punishment are you worried about?  I really don't think you'll be
> able to measure any performance impact.
>
> I agree that the x86 code you add *is* simpler than the generic
> version.  But I think the *overall* complexity is higher because now
> you have to look at two versions (generic and x86) and convince
> yourself that it's safe to use the x86 version.
>

fine, i will that patch.

Yinghai
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