From: "H. Peter Anvin" <hpa@zytor.com>
To: Yinghai Lu <yinghai@kernel.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
Andrew Morton <akpm@linux-foundation.org>,
Jesse Brandeburg <jesse.brandeburg@intel.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 5/5] x86: update nr_irqs according cpu num
Date: Fri, 08 Jan 2010 13:11:57 -0800 [thread overview]
Message-ID: <4B479F9D.7060907@zytor.com> (raw)
In-Reply-To: <86802c441001081206r1df18abdhbb9a882868cc6b39@mail.gmail.com>
On 01/08/2010 12:06 PM, Yinghai Lu wrote:
>>>
>>> Ouch! Unless I misread this code this will leave nr_irqs at
>>> NR_IRQS_LEGACY. aka 16.
>>>
>>> Let's do something stupid and simple.
>>> nr_irqs = nr_cpus_ids * 256; /* Semi-arbitrary number */
>>
>> This would be 1048576 on the biggest machines we currently support.
>> Now, the number of IRQ *vectors* is limited to
>> (224-system vectors)*(cpu count), so one could argue that if there is
>> anything that is not semi-arbitrary it would be that number, but that
>> doesn't account for vector sharing.
>
> (256 - 32 - 16 - system_vectors) * cpu_count + 16
>
> the 16 is legacy from IRQ0 to 15 has domain with all cpus set.
>
... assuming you're on a platform with a legacy PIC. I would like to
see the legacy PIC hard-coded assumptions to go away, and instead be
done as runtime allocations on the relevant platforms.
> some interface in /proc/interrupts need it to make sure sth in sequence.
I can't even parse this sentence, never mind figuring out what it would
mean. Certainly there is a better way to do that?
-hpa
next prev parent reply other threads:[~2010-01-08 21:21 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-08 11:53 [PATCH 1/5] irq: remove not need bootmem code Yinghai Lu
2010-01-08 11:53 ` [PATCH 2/5] radix: move radix init early Yinghai Lu
2010-01-08 11:53 ` [PATCH 3/5] sparseirq: change irq_desc_ptrs to static Yinghai Lu
2010-01-08 11:53 ` [PATCH 4/5] sparseirq: use radix_tree instead of ptrs array Yinghai Lu
2010-01-08 12:14 ` Cyrill Gorcunov
2010-01-08 18:43 ` Eric W. Biederman
2010-01-08 11:53 ` [PATCH 5/5] x86: update nr_irqs according cpu num Yinghai Lu
2010-01-08 19:11 ` Eric W. Biederman
2010-01-08 19:21 ` H. Peter Anvin
2010-01-08 20:06 ` Yinghai Lu
2010-01-08 21:11 ` H. Peter Anvin [this message]
2010-01-08 20:10 ` Eric W. Biederman
2010-01-08 21:15 ` H. Peter Anvin
2010-01-08 19:49 ` Yinghai Lu
2010-01-08 20:20 ` Eric W. Biederman
2010-01-08 20:43 ` Yinghai Lu
2010-01-08 18:52 ` [PATCH 1/5] irq: remove not need bootmem code Eric W. Biederman
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