linux-kernel - Re: [PATCH] print vmalloc() state after allocation failures

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Message-ID: <20110408001942.GC2874@cmpxchg.org>
Date:	Thu, 7 Apr 2011 17:19:42 -0700
From:	Johannes Weiner <hannes@...xchg.org>
To:	Dave Hansen <dave@...ux.vnet.ibm.com>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] print vmalloc() state after allocation failures

On Thu, Apr 07, 2011 at 10:23:02AM -0700, Dave Hansen wrote:
> Signed-off-by: Dave Hansen <dave@...ux.vnet.ibm.com>

I agree with this in general, but have some nitpicks.

> @@ -1579,6 +1579,18 @@ static void *__vmalloc_area_node(struct 
>  	return area->addr;
>  
>  fail:
> +	if (!(gfp_mask & __GFP_NOWARN) && printk_ratelimit()) {

There is a comment above the declaration of printk_ratelimit:

/*
 * Please don't use printk_ratelimit(), because it shares ratelimiting state
 * with all other unrelated printk_ratelimit() callsites.  Instead use
 * printk_ratelimited() or plain old __ratelimit().
 */

I realize that the page allocator does it the same way, but I think it
should probably be fixed in there, rather than spread any further.

> +		/*
> +		 * We probably did a show_mem() and a stack dump above
> +		 * inside of alloc_page*().  This is only so we can
> +		 * tell how big the vmalloc() really was.  This will
> +		 * also not be exactly the same as what was passed
> +		 * to vmalloc() due to alignment and the guard page.
> +		 */
> +		printk(KERN_WARNING "%s: vmalloc: allocation failure, "
> +			"allocated %ld of %ld bytes\n", current->comm,
> +			(area->nr_pages*PAGE_SIZE), area->size);
> +	}

To me, this does not look like something that should just be appended
to the whole pile spewed out by dump_stack() and show_mem().  What do
you think about doing the page allocation with __GFP_NOWARN and have
the full report come from this place, with the line you introduce as
leader?

	Hannes
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