linux-kernel - Re: [PATCH] X86: Change the default value of nr_irqs from 32 to NR

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Date:	Tue, 19 Aug 2008 19:32:03 +0100
From:	Alex Nixon <alex.nixon@...rix.com>
To:	Yinghai Lu <yhlu.kernel@...il.com>
CC:	Ingo Molnar <mingo@...e.hu>,
	Jeremy Fitzhardinge <Jeremy.Fitzhardinge@...rix.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] X86: Change the default value of nr_irqs from 32 to NR_IRQs

Yinghai Lu wrote:
> On Tue, Aug 19, 2008 at 11:13 AM, Alex Nixon (Intern)
> <Alex.Nixon@...rix.com> wrote:
>> Yinghai Lu <yhlu.kernel@...il.com> wrote:
>>> On Tue, Aug 19, 2008 at 9:55 AM, Alex Nixon <alex.nixon@...rix.com> wrote:
>>>> If the number of discovered IRQs is suspiciously low, this patch causes
>>>> the number reported to default to NR_IRQS, rather than 32.  NR_IRQS has
>>>> already been defined to be a >sensible value for the current system (in
>>>> particular, at least 224 when paravirtualisation is involved).
>>>>
>>> if only one ioapic, nr will be 24<<1, you will get 48. Does pv has io apic
>>> ?
>>>
>>> YH
>>>
>> I'm not sure about the general case, but Xen does not (Jeremy correct me if
>> I'm wrong).
>>
>> Unless I'm missing something (which I may well be; I'm new to this area of
>> code), it seems more logical anyway to default back to the calculated
>> system-specific value (NR_IRQS), instead of 32, which seems rather
>> arbitrary.
> 
> can you try !CONFIG_HAVE_SPARSE_IRQ and CONFIG_HAVE_SPARSE_IRQ ?
> 
> YH

Sorry I should have mentioned originally - the bug occurs both with 
CONFIG_HAVE_SPARSE_IRQ enabled, and disabled.

- Alex
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