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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: Dave Hansen <dave@linux.vnet.ibm.com>
Subject: Re: [RFCv2][PATCH] add some drop_caches documentation and info messsge
Cc: kosaki.motohiro@jp.fujitsu.com, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, lnxninja@linux.vnet.ibm.com,
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Date: Tue, 21 Sep 2010 09:57:31 +0900 (JST)
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> On Fri, 2010-09-17 at 09:26 +0900, KOSAKI Motohiro wrote:
> > > diff -puN fs/drop_caches.c~update-drop_caches-documentation fs/drop_caches.c
> > > --- linux-2.6.git/fs/drop_caches.c~update-drop_caches-documentation	2010-09-16 09:43:52.000000000 -0700
> > > +++ linux-2.6.git-dave/fs/drop_caches.c	2010-09-16 09:43:52.000000000 -0700
> > > @@ -47,6 +47,8 @@ int drop_caches_sysctl_handler(ctl_table
> > >  {
> > >  	proc_dointvec_minmax(table, write, buffer, length, ppos);
> > >  	if (write) {
> > > +		printk(KERN_NOTICE "%s (%d): dropped kernel caches: %d\n",
> > > +			current->comm, task_pid_nr(current), sysctl_drop_caches);
> > >  		if (sysctl_drop_caches & 1)
> > >  			iterate_supers(drop_pagecache_sb, NULL);
> > >  		if (sysctl_drop_caches & 2)
> > 
> > Can't you print it only once?
> 
> Sure.  But, I also figured that somebody calling it every minute is
> going to be much more interesting than something just on startup.
> Should we printk_ratelimit() it, perhaps?

Umm...

every minute drop_caches + printk_ratelimit() mean every drop_caches output
printk(). It seems annoying. I'm worry about that I'll see drop_caches's printk fill
my syslog.

But, It is not strong opinion. Because I don't use every minute drop_caches, then
I have no experience such usecase. It's up to you.