linux-kernel - Re: [PATCH 2/3] profile: Suppress warning about large allocations when profile=1 is specified

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Date:	Thu, 16 Jul 2009 11:37:19 +0100
From:	Mel Gorman <mel@....ul.ie>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Linux Memory Management List <linux-mm@...ck.org>,
	Heinz Diehl <htd@...cy-poultry.org>,
	David Miller <davem@...emloft.net>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [PATCH 2/3] profile: Suppress warning about large allocations
	when profile=1 is specified

On Thu, Jul 16, 2009 at 10:12:20AM +0900, KOSAKI Motohiro wrote:
> > When profile= is used, a large buffer is allocated early at boot. This
> > can be larger than what the page allocator can provide so it prints a
> > warning. However, the caller is able to handle the situation so this patch
> > suppresses the warning.
> 
> I'm confused.
> 
> Currently caller doesn't handle error return.
> 
> ----------------------------------------------------------
> asmlinkage void __init start_kernel(void)
> {
> (snip)
>         init_timers();
>         hrtimers_init();
>         softirq_init();
>         timekeeping_init();
>         time_init();
>         sched_clock_init();
>         profile_init();           <-- ignore return value
> ------------------------------------------------------------
> 
> and, if user want to use linus profiler, the user should choice select
> proper bucket size by boot parameter.
> Currently, allocation failure message tell user about specified bucket size
> is wrong.
> I think this patch hide it.
> 

Look at what profile_init() itself is doing. You can't see it from the
patch context but when alloc_pages_exact() fails, it calls vmalloc(). If
that fails, profiling is just disabled. There isn't really anything the
caller of profile_init() can do about it and the page allocator doesn't
need to scream about it.

> 
> > 
> > Signed-off-by: Mel Gorman <mel@....ul.ie>
> > ---
> >  kernel/profile.c |    5 +++--
> >  1 files changed, 3 insertions(+), 2 deletions(-)
> > 
> > diff --git a/kernel/profile.c b/kernel/profile.c
> > index 69911b5..419250e 100644
> > --- a/kernel/profile.c
> > +++ b/kernel/profile.c
> > @@ -117,11 +117,12 @@ int __ref profile_init(void)
> >  
> >  	cpumask_copy(prof_cpu_mask, cpu_possible_mask);
> >  
> > -	prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL);
> > +	prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL|__GFP_NOWARN);
> >  	if (prof_buffer)
> >  		return 0;
> >  
> > -	prof_buffer = alloc_pages_exact(buffer_bytes, GFP_KERNEL|__GFP_ZERO);
> > +	prof_buffer = alloc_pages_exact(buffer_bytes,
> > +					GFP_KERNEL|__GFP_ZERO|__GFP_NOWARN);
> >  	if (prof_buffer)
> >  		return 0;
> 
> 
> 

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab
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