linux-kernel - Re: [patch] drop_caches: add some documentation and info message

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Message-Id: <20140207123129.84f9fb0aaf32f0e09c78851a@linux-foundation.org>
Date:	Fri, 7 Feb 2014 12:31:29 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Rik van Riel <riel@...hat.com>, Dave Hansen <dave@...1.net>,
	Michal Hocko <mhocko@...e.cz>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [patch] drop_caches: add some documentation and info message

On Fri, 7 Feb 2014 13:13:32 -0500 Johannes Weiner <hannes@...xchg.org> wrote:

> @@ -63,6 +64,9 @@ int drop_caches_sysctl_handler(ctl_table *table, int write,
>  			iterate_supers(drop_pagecache_sb, NULL);
>  		if (sysctl_drop_caches & 2)
>  			drop_slab();
> +		printk_ratelimited(KERN_INFO "%s (%d): dropped kernel caches: %d\n",
> +				   current->comm, task_pid_nr(current),
> +				   sysctl_drop_caches);
>  	}
>  	return 0;
>  }

My concern with this is that there may be people whose
other-party-provided software uses drop_caches.  Their machines will
now sit there emitting log messages and there's nothing they can do
about it, apart from whining at their vendors.


We could do something like this?

--- a/fs/drop_caches.c~drop_caches-add-some-documentation-and-info-message-fix
+++ a/fs/drop_caches.c
@@ -60,13 +60,17 @@ int drop_caches_sysctl_handler(ctl_table
 	if (ret)
 		return ret;
 	if (write) {
+		static int stfu;
+
 		if (sysctl_drop_caches & 1)
 			iterate_supers(drop_pagecache_sb, NULL);
 		if (sysctl_drop_caches & 2)
 			drop_slab();
-		printk_ratelimited(KERN_INFO "%s (%d): dropped kernel caches: %d\n",
-				   current->comm, task_pid_nr(current),
-				   sysctl_drop_caches);
+		stfu |= sysctl_drop_caches & 4;
+		if (!stfu)
+			pr_info_ratelimited("%s (%d): dropped kernel caches: %d\n",
+					   current->comm, task_pid_nr(current),
+					   sysctl_drop_caches);
 	}
 	return 0;
 }
_

(note switch to pr_info_ratelimited)
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