linux-kernel - Re: [PATCH 0/3] dyn

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Date:	Thu, 31 Jul 2008 11:21:08 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Mike Travis" <travis@....com>
Cc:	"Ingo Molnar" <mingo@...e.hu>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Dhaval Giani" <dhaval@...ux.vnet.ibm.com>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, "Jack Steiner" <steiner@....com>
Subject: Re: [PATCH 0/3] dyn_array support #2

On Thu, Jul 31, 2008 at 9:32 AM, Mike Travis <travis@....com> wrote:
> Yinghai Lu wrote:
>> please check the patches adding dyn_array and nr_irqs #2
>>
>> Thanks
>>
>> YH
>
>
> It appears that the primary difference between your patch and Eric's
> is that you estimate the number of IRQ's required based on the number
> of cpus present, while Eric's patch grows the list based on the IRQ's
> being requested.  For soon to be "power" desktop systems (say dual 8 core
> Nahalem's w/HT), you're reserving IRQ's for 32 cpus on a system which
> probably has one I/O bus (or maybe two).  A dual socket Larabbee system
> will have 256 cpus.  An SGI UV system has more of a "building block"
> approach, where you can grow all three (cpus, memory, I/O) independently.
>
> One other very nice feature of Eric's approach is that the new "IRQ"
> struct being requested can be created in "node local" memory, cutting
> down significantly the number of "cross node" accesses.

where is Eric's patch? I didn't get it...

>
> Plus, I still like Ingo's suggestion to not change NR_IRQS ==> nr_irqs.
> CONFIG_ARCH_HAS_DYNAMIC_IRQS spells out exactly what NR_IRQS means.
> (Even more accurate would be CONFIG_ARCH_HAS_DYNAMIC_NR_IRQS.)

not every array need to be changed to dyn_array, if the static array
is not big enough.
and some DEFINE_BIT map is using NR_IRQS.

>
> The DEFINE_DYN_ARRAY could be the following.  (Changing general purpose
> DYN_ARRAY to specifically purposed IRQ_ARRAY.)

dyn_array is some more generic, and nr_irqs is one of it's user

>
> #ifdef CONFIG_ARCH_HAS_DYNAMIC_IRQS
> #define DEFINE_IRQ_ARRAY <new variable irq array [or list] definition>
> #else
> #define DEFINE_IRQ_ARRAY <old static irq array>
> #endif
>
> For the immediate problem, unraveling the code merge back to IRQ's based
> on NR_IOAPICS would seem to be the least intrusive.

less intrusive way could be use dyn_array and make nr_irqs to be set
via acpi_madt_oem_check...

YH
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