linux-kernel - Re: [PATCH] mm: Drop "PFNs busy" printk in an expected path.

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Date:   Thu, 29 Dec 2016 10:12:57 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Eric Anholt <eric@...olt.net>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-stable <stable@...r.kernel.org>,
        "Robin H. Johnson" <robbat2@...is-terrarum.net>,
        Michal Nazarewicz <mina86@...a86.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [PATCH] mm: Drop "PFNs busy" printk in an expected path.

This has been already brought up
http://lkml.kernel.org/r/20161130092239.GD18437@dhcp22.suse.cz and there
was a proposed patch for that which ratelimited the output
http://lkml.kernel.org/r/20161130132848.GG18432@dhcp22.suse.cz resp.
http://lkml.kernel.org/r/robbat2-20161130T195244-998539995Z@orbis-terrarum.net

then the email thread just died out because the issue turned out to be a
configuration issue. Michal indicated that the message might be useful
so dropping it completely seems like a bad idea. I do agree that
something has to be done about that though. Can we reconsider the
ratelimit thing?

On Wed 28-12-16 18:31:31, Eric Anholt wrote:
> For CMA allocations, we expect to occasionally hit this error path, at
> which point CMA will retry.  Given that, we shouldn't be spamming
> dmesg about it.
> 
> The Raspberry Pi graphics driver does frequent CMA allocations, and
> during regression testing this printk was sometimes occurring 100s of
> times per second.
> 
> Signed-off-by: Eric Anholt <eric@...olt.net>
> Cc: linux-stable <stable@...r.kernel.org>
> ---
>  mm/page_alloc.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 6de9440e3ae2..bea7204c14a5 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -7289,8 +7289,6 @@ int alloc_contig_range(unsigned long start, unsigned long end,
>  
>  	/* Make sure the range is really isolated. */
>  	if (test_pages_isolated(outer_start, end, false)) {
> -		pr_info("%s: [%lx, %lx) PFNs busy\n",
> -			__func__, outer_start, end);
>  		ret = -EBUSY;
>  		goto done;
>  	}
> -- 
> 2.11.0
> 
> --
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-- 
Michal Hocko
SUSE Labs