linux-kernel - Re: [RFC Patch 2/2] mm: Add parameters to limit a rate of outputting memory error messages

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Date:	Thu, 11 Apr 2013 03:32:04 -0400
From:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
To:	Mitsuhiro Tanino <mitsuhiro.tanino.gm@...achi.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>
Subject: Re: [RFC Patch 2/2] mm: Add parameters to limit a rate of outputting
 memory error messages

On Thu, Apr 11, 2013 at 12:59:38AM -0400, Naoya Horiguchi wrote:
> Hi Tanino-san,
> 
> On Thu, Apr 11, 2013 at 12:27:15PM +0900, Mitsuhiro Tanino wrote:
> > This patch introduces new sysctl interfaces in order to limit
> > a rate of outputting memory error messages.
> > 
> > - vm.memory_failure_print_ratelimit:
> >   Specify the minimum length of time between messages.
> >   By default the rate limiting is disabled.
> > 
> > - vm.memory_failure_print_ratelimit_burst:
> >   Specify the number of messages we can send before rate limiting.
> > 
> > Signed-off-by: Mitsuhiro Tanino <mitsuhiro.tanino.gm@...achi.com>
...
> > @@ -78,6 +79,16 @@ EXPORT_SYMBOL_GPL(hwpoison_filter_dev_minor);
> >  EXPORT_SYMBOL_GPL(hwpoison_filter_flags_mask);
> >  EXPORT_SYMBOL_GPL(hwpoison_filter_flags_value);
> >  
> > +/*
> > + * This enforces a rate limit for outputting error message.
> > + * The default interval is set to "0" HZ. This means that
> > + * outputting error message is not limited by default.
> > + * The default burst is set to "10". This parameter can control
> > + * to output number of messages per interval.
> > + * If interval is set to "0", the burst is ineffective.
> > + */
> > +DEFINE_RATELIMIT_STATE(sysctl_memory_failure_print_ratelimit, 0 * HZ, 10);
> > +
> >  static int hwpoison_filter_dev(struct page *p)
> >  {
> >  	struct address_space *mapping;
> > @@ -622,13 +633,16 @@ static int me_pagecache_dirty(struct page *p, unsigned long pfn)
> >  	SetPageError(p);
> >  	if (mapping) {
> >  		/* Print more information about the file. */
> > -		if (mapping->host != NULL && S_ISREG(mapping->host->i_mode))
> > -			pr_info("MCE %#lx: File was corrupted: Dev:%s Inode:%lu Offset:%lu\n",
> > -				page_to_pfn(p), mapping->host->i_sb->s_id,
> > -				mapping->host->i_ino, page_index(p));
> > -		else
> > -			pr_info("MCE %#lx: A dirty page cache was corrupted.\n",
> > -				page_to_pfn(p));
> > +		if (__ratelimit(&sysctl_memory_failure_print_ratelimit)) {
> > +			if (mapping->host != NULL &&
> > +			    S_ISREG(mapping->host->i_mode))
> > +				pr_info("MCE %#lx: File was corrupted: Dev:%s Inode:%lu Offset:%lu\n",
> > +				   page_to_pfn(p), mapping->host->i_sb->s_id,
> > +				   mapping->host->i_ino, page_index(p));
> > +			else
> > +				pr_info("MCE %#lx: A dirty page cache was corrupted.\n",
> > +					page_to_pfn(p));
> > +		}
> >  
> >  		/*
> >  		 * IO error will be reported by write(), fsync(), etc.

I don't think it's enough to do ratelimit only for me_pagecache_dirty().
When tons of memory errors flood, all of printk()s in memory error handler
can print out tons of messages.

Thanks,
Naoya
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