linux-kernel - Re: [PATCH] irq: optimize init_kstat_irqs/init_copy_kstat

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Message-ID: <498FECD3.9030204@kernel.org>
Date:	Mon, 09 Feb 2009 00:44:03 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Andrew Morton <akpm@...ux-foundation.org>, tglx@...utronix.de,
	hpa@...or.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] irq: optimize init_kstat_irqs/init_copy_kstat_irqs

Ingo Molnar wrote:
> * Andrew Morton <akpm@...ux-foundation.org> wrote:
> 
>> On Mon, 9 Feb 2009 09:11:24 +0100 Ingo Molnar <mingo@...e.hu> wrote:
>>
>>> * Andrew Morton <akpm@...ux-foundation.org> wrote:
>>>
>>>> On Sat, 7 Feb 2009 01:01:03 -0800 Yinghai Lu <yinghai@...nel.org> wrote:
>>>>
>>>>> add kzalloc_node_safe()?
>>>> I cannot find that function.
>>> His suggestion is to provide that allocator variant.
>>>
>> Oh.
>>
>> It isn't possible to write a kzalloc_node_safe(GFP_ATOMIC).  Or at
>> least, we've never worked out a way.
>>
>> Maybe I'm confused again.
> 
> Indeed - duh - more morning tea needed.
> 
> Yinghai, why are those allocations GFP_ATOMIC to begin with? These:
> 
> earth4:~/tip> grep GFP_ATOMIC kernel/irq/*.c
> kernel/irq/handle.c:	ptr = kzalloc_node(nr * sizeof(*desc->kstat_irqs), GFP_ATOMIC, node);
> kernel/irq/handle.c:	desc = kzalloc_node(sizeof(*desc), GFP_ATOMIC, node);
> kernel/irq/manage.c:	action = kmalloc(sizeof(struct irqaction), GFP_ATOMIC);
> 
> Should all be GFP_KERNEL. Wherever they are within a spinlocked section the code 
> should be restructured. All descriptor data structures should be preallocated at 
> __setup_irq() time. If we ever need to allocate dynamically later on, in the middle 
> of some difficult codepath that's a structure bug in the code.

ok.

> 
> and this one:
> 
> kernel/irq/numa_migrate.c:	desc = kzalloc_node(sizeof(*desc), GFP_ATOMIC, node);
> 
> should fail the migration silently if GFP_ATOMIC returns NULL.
it will reuse the old one.

YH
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