linux-kernel - Re: [PATCH] slub - Use local

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Message-ID: <Pine.LNX.4.64.0709121522280.3835@schroedinger.engr.sgi.com>
Date:	Wed, 12 Sep 2007 15:28:10 -0700 (PDT)
From:	Christoph Lameter <clameter@....com>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
cc:	Peter Zijlstra <peterz@...radead.org>, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, mingo@...hat.com,
	linux-ia64@...r.kernel.org
Subject: Re: [PATCH] slub - Use local_t protection

On Wed, 5 Sep 2007, Mathieu Desnoyers wrote:

> Use local_enter/local_exit for protection in the fast path.

Sorry that it took some time to get back to this issue. KS interfered.

> @@ -1494,8 +1487,16 @@ new_slab:
>  		c->page = new;
>  		goto load_freelist;
>  	}
> -
> +	if (gfpflags & __GFP_WAIT) {
> +		local_nest_irq_enable();
> +		local_exit();
> +	}
>  	new = new_slab(s, gfpflags, node);
> +	if (gfpflags & __GFP_WAIT) {
> +		local_enter();
> +		local_nest_irq_disable();
> +	}
> +
>  	if (new) {
>  		c = get_cpu_slab(s, smp_processor_id());
>  		if (c->page) {

Hmmmm... Definitely an interesting change to move the interrupt 
enable/disable to __slab_alloc. But it looks like it is getting a bit 
messy. All my attempts ended also like this. Sigh.

> @@ -2026,8 +2032,11 @@ static struct kmem_cache_node *early_kme
>  
>  	BUG_ON(kmalloc_caches->size < sizeof(struct kmem_cache_node));
>  
> +	if (gfpflags & __GFP_WAIT)
> +		local_irq_enable();
>  	page = new_slab(kmalloc_caches, gfpflags, node);
> -
> +	if (gfpflags & __GFP_WAIT)
> +		local_irq_disable();
>  	BUG_ON(!page);
>  	if (page_to_nid(page) != node) {
>  		printk(KERN_ERR "SLUB: Unable to allocate memory from "

Hmmmm... Actually we could drop the irq disable / enable here since this 
is boot code. That would also allow the removal of the later 
local_irq_enable.

Good idea. I think I will do the moving of the interrupt enable/disable 
independently.

-
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