linux-kernel - Re: [PATCH] x86: add show

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Date:	Sun, 27 Sep 2009 14:28:05 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Yinghai Lu <yinghai@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: add show_lapic=

[Cyrill Gorcunov - Sun, Sep 27, 2009 at 12:54:06PM +0400]
| [Yinghai Lu - Sun, Sep 27, 2009 at 01:29:22AM -0700]
| | Cyrill Gorcunov wrote:
| | > [Yinghai Lu - Sun, Sep 27, 2009 at 12:01:52AM -0700]
| | > | 
| | > | so could use that together with apci=debug to print less cpu apic.
| | > | 
| | > | otherwise for system have more cpus will take a while
| | > | 
| | > | also move apic_verbosity check to print_all_ICs
| | > | 
| | > | Signed-off-by: Yinghai Lu <yinghai@...nel.org>
| | > | 
| | > | ---
| | > |  arch/x86/kernel/apic/io_apic.c |   42 ++++++++++++++++++++++++++---------------
| | > |  1 file changed, 27 insertions(+), 15 deletions(-)
| | > ...
| | > 
| | > Hi Yinghai, good idea!
| | > 
| | > I've tuned your patch a bit together with changelog.
| | > 
| | > 1) show_lapic=1 by default does change current kernel behaviour
| | >    so it should be set to max cpu available.
| | 
| | think about system with lots of cpu. but i still want to use apic=debug
| 
| but you should not change current behaviour. starting with this change
| I'll get only first apic dump, so if I don;t know how many apics I have
| what the number I should pass? Does it mean I would need to
| pass say show_lapic=2, or 4, or 6 or whatever  _all-the-time_ to be sure
| my Core2Duo prints all lapics?
| 
| | 
| | > 2) show_lapic contains the max number of lapics being printed
| | >    so we need to count them instead of plain comparation with
| | >    cpu number, as a result I've changed print_local_APICs. Or
| | >    you meant _exactly_ cpuid number? In meaning like
| | >    show_lapic=max_cpuid. Hmm?
| | > 
| | your change anything about that. there is not gap between cpu id.
| 
| you walk with for_each_online_cpu with is not the same
| as for_each_present_cpu. yes, at this stage we hardly get
| the situation when cpu initialized and then suddenly get
| offline status but anyway
| 
| | 
| | YH
| | 
| 	-- Cyrill

Also and your and my "update" (that named :-) missed the fact that get_option
may return without set argument at all, so num should be explicitly
initialized as well (in setup_show_lapic).

	-- Cyrill
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