linux-kernel - Re: [PATCH] vmscan: add task name to warn_scan

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Message-ID: <alpine.DEB.2.00.1111222230270.21009@chino.kir.corp.google.com>
Date:	Tue, 22 Nov 2011 22:32:45 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Minchan Kim <minchan.kim@...il.com>
cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Johannes Weiner <jweiner@...hat.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] vmscan: add task name to warn_scan_unevictable()
 messages

On Wed, 23 Nov 2011, Minchan Kim wrote:

> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index a1893c0..29d163e 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -3448,9 +3448,10 @@ void scan_mapping_unevictable_pages(struct address_space *mapping)
> >  static void warn_scan_unevictable_pages(void)
> >  {
> >  	printk_once(KERN_WARNING
> > -		    "The scan_unevictable_pages sysctl/node-interface has been "
> > +		    "%s: The scan_unevictable_pages sysctl/node-interface has been "
> >  		    "disabled for lack of a legitimate use case.  If you have "
> > -		    "one, please send an email to linux-mm@...ck.org.\n");
> > +		    "one, please send an email to linux-mm@...ck.org.\n",
> > +		    current->comm);
> >  }
> 
> Just nitpick:
> How about using WARN_ONCE instead of custom warning?
> It can show more exact call path as well as comm.
> I guess it's more noticible to users.
> Anyway, either is okay to me.
> 

When I used WARN_ONCE() to notify users that /proc/pid/oom_adj was 
deprecated, people complained that it triggered userspace log parsers 
thinking that there's a serious problem and it adds a taint flag so it got 
reverted.  I'd recommend keeping it printk_once().
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