linux-kernel - Re: Warn when we run out of swap space (was Re: Misleading OOM messages)

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Message-ID: <20090522145634.GA27257@elf.ucw.cz>
Date:	Fri, 22 May 2009 16:56:34 +0200
From:	Pavel Machek <pavel@....cz>
To:	Christoph Lameter <cl@...ux-foundation.org>
Cc:	Dave Hansen <dave@...ux.vnet.ibm.com>,
	David Rientjes <rientjes@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Nick Piggin <npiggin@...e.de>, Mel Gorman <mel@....ul.ie>,
	Peter Ziljstra <a.p.ziljstra@...llo.nl>,
	San Mehat <san@...roid.com>, Arve Hj?nnev?g <arve@...roid.com>,
	linux-kernel@...r.kernel.org
Subject: Re: Warn when we run out of swap space (was Re: Misleading OOM
	messages)

On Fri 2009-05-22 10:17:15, Christoph Lameter wrote:
> 
> Subject: Warn if we run out of swap space
> 
> Running out of swap space means that the evicton of anonymous pages may no longer
> be possible which can lead to OOM conditions.
> 
> Print a warning when swap space first becomes exhausted.
> 
> Signed-off-by: Christoph Lameter <cl@...ux-foundation.org>

WARN_ONCE... will it mean a backtrace? That's quite an overkill for
something that is not a kernel fault (and where backtrace is useless).

But  yes, I agree in principle.
									Pavel

> @@ -412,6 +412,7 @@ swp_entry_t get_swap_page(void)
>  	nr_swap_pages++;
>  noswap:
>  	spin_unlock(&swap_lock);
> +	WARN_ONCE(1, "All of swap is in use. Some pages cannot be swapped out.");
>  	return (swp_entry_t) {0};
>  }

-- 
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