From: "H. Peter Anvin" <hpa@zytor.com>
To: mingo@kernel.org, hpa@zytor.com, agordeev@redhat.com,
linux-kernel@vger.kernel.org, yinghai@kernel.org,
suresh.b.siddha@intel.com, tglx@linutronix.de
Cc: linux-tip-commits@vger.kernel.org
Subject: Re: [tip:x86/apic] x86/apic: Try to spread IRQ vectors to different priority levels
Date: Wed, 20 Jun 2012 10:23:39 -0700 [thread overview]
Message-ID: <4FE2071B.5040602@zytor.com> (raw)
In-Reply-To: <tip-1bccd58bfffc5a677051937b332b71f0686187c1@git.kernel.org>
On 06/08/2012 07:50 AM, tip-bot for Alexander Gordeev wrote:
> Commit-ID: 1bccd58bfffc5a677051937b332b71f0686187c1
> Gitweb: http://git.kernel.org/tip/1bccd58bfffc5a677051937b332b71f0686187c1
> Author: Alexander Gordeev <agordeev@redhat.com>
> AuthorDate: Thu, 7 Jun 2012 15:15:15 +0200
> Committer: Ingo Molnar <mingo@kernel.org>
> CommitDate: Fri, 8 Jun 2012 11:44:28 +0200
>
> x86/apic: Try to spread IRQ vectors to different priority levels
>
> When assigning a new vector it is primarially done by adding 8
> to the previously given out vector number. Hence, two
> consequently allocated vector numbers would likely fall into the
> same priority level. Try to spread vector numbers to different
> priority levels better by changing the step from 8 to 16.
>
OK, stupid question: WHY?
In general, in Linux the random prioritization is actually a negative.
The only reason for the spreading by 8 is because of bugs/misfeatures in
old APIC implementations which made them handle more than two interrupts
per priority level rather inefficiently.
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
next prev parent reply other threads:[~2012-06-20 17:23 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-05 11:23 [PATCH 4/8] x86: apic: Factor out default vector_allocation_domain() operations Alexander Gordeev
2012-06-06 8:22 ` Ingo Molnar
2012-06-06 8:42 ` Alexander Gordeev
2012-06-07 13:14 ` [PATCH 4/8] x86/apic: Factor out default vector_allocation_domain() operation Alexander Gordeev
2012-06-07 22:24 ` Suresh Siddha
2012-06-08 14:49 ` [tip:x86/apic] " tip-bot for Alexander Gordeev
2012-06-07 13:15 ` [PATCH 5/8] x86/apic: Try to spread IRQ vectors to different priority levels Alexander Gordeev
2012-06-07 22:26 ` Suresh Siddha
2012-06-08 14:50 ` [tip:x86/apic] " tip-bot for Alexander Gordeev
2012-06-20 17:23 ` H. Peter Anvin [this message]
2012-06-20 21:41 ` Suresh Siddha
2012-06-20 21:46 ` H. Peter Anvin
2012-06-07 13:15 ` [PATCH 6/8] x86/apic: Avoid useless scanning thru a cpumask in assign_irq_vector() Alexander Gordeev
2012-06-07 22:28 ` Suresh Siddha
2012-06-08 14:51 ` [tip:x86/apic] " tip-bot for Alexander Gordeev
2012-06-07 13:15 ` [PATCH 7/8] x86/apic: Make cpu_mask_to_apicid() operations return error code Alexander Gordeev
2012-06-07 22:24 ` Suresh Siddha
2012-06-08 15:15 ` Alexander Gordeev
2012-06-08 16:53 ` [PATCH] x86/apic: Eliminate cpu_mask_to_apicid() operation Alexander Gordeev
2012-06-08 18:24 ` Suresh Siddha
2012-06-08 22:36 ` Yinghai Lu
2012-06-11 8:22 ` Ingo Molnar
2012-06-11 10:51 ` Alexander Gordeev
2012-06-08 14:51 ` [tip:x86/apic] x86/apic: Make cpu_mask_to_apicid() operations return error code tip-bot for Alexander Gordeev
2012-06-07 13:16 ` [PATCH 8/8] x86/apic: Make cpu_mask_to_apicid() operations check cpu_online_mask Alexander Gordeev
2012-06-08 14:52 ` [tip:x86/apic] " tip-bot for Alexander Gordeev
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