From: "Martin J. Bligh" <Martin.Bligh@us.ibm.com>
To: Manfred Spraul <manfred@colorfullife.com>,
linux-kernel@vger.kernel.org,
Sean Cavanaugh <seanc@gearboxsoftware.com>
Subject: Re: P4 SMP load balancing
Date: Fri, 12 Oct 2001 14:38:44 -0700 [thread overview]
Message-ID: <2170144124.1002897524@mbligh.des.sequent.com> (raw)
In-Reply-To: <3BC738AD.A0329BBF@colorfullife.com>
>> > ovendev:~# cat /proc/interrupts
>> > CPU0 CPU1
>> > 0: 6348212 0 IO-APIC-edge timer
>> > 1: 2 0 IO-APIC-edge keyboard
>> > 2: 0 0 XT-PIC cascade
>> > 8: 1 0 IO-APIC-edge rtc
>> > 9: 0 0 IO-APIC-edge acpi
>> > 16: 92620 0 IO-APIC-level eth0
>> > 18: 5085 0 IO-APIC-level aic7xxx, aic7xxx
>> > NMI: 0 0
>> > LOC: 6348388 6348427
>> > ERR: 0
>> > MIS: 0
>>
>> I don't think this should happen. In the event of both procs having equal
>> priority (linux never changes them, so they always do), we should fall back
>> to the arbitration priority of the lapic. Whether you have 1 or 2 I/O apics
>> working shouldn't make a difference.
>
> The P 4 has a new apic, and lowest priority delivery doesn't work
> anymore.
>
> <<<<<<< Chapter 7.6.10 of 24547202.pdf
> In operating systems that use the lowest priority interrupt delivery
> mode
> but do not update the TPR, the TPR information saved in the chipset will
> potentially cause the interrupt to be always delivered to the same
> processor from the logical set. This behavior is functionally backward
> compatible with the P6 family processor but may result in unexpected
> performance implications.
> <<<<<<< (search for 245472 on google for the pdf file)
Ick. Thanks for pointing this out ... will go read the P4 docs closer.
Someone here has patches to set the TPR properly, but they weren't
giving the performance gain we'd hoped for. In light of this, they'd
probably help out much more on the P4. I'll see if I can persuade them
to publish ...
M.
next prev parent reply other threads:[~2001-10-12 21:41 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-10-12 18:38 P4 SMP load balancing Manfred Spraul
2001-10-12 21:38 ` Martin J. Bligh [this message]
-- strict thread matches above, loose matches on Subject: below --
2001-10-12 9:28 Sean Cavanaugh
2001-10-12 17:59 ` Martin J. Bligh
2001-10-14 9:07 ` Sean Cavanaugh
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