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To: util-linux@vger.kernel.org
From: "U.Mutlu" <for-gmane@mutluit.com>
Subject: Re: fsck memory leak
Date: Fri, 4 Dec 2015 20:09:38 +0100
Message-ID: <n3sodi$qhv$1@ger.gmane.org>
References: <n3rei3$8l3$1@ger.gmane.org> <20151204151927.GA3548@thunk.org>
 <n3sjvh$ib8$1@ger.gmane.org>
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U.Mutlu wrote on 12/04/2015 06:53 PM:
> Theodore Ts'o wrote on 12/04/2015 04:19 PM:
>> On Fri, Dec 04, 2015 at 08:15:14AM +0100, U.Mutlu wrote:
>>> Hi,
>>> when I as root do "touch /forcefsck" and reboot, then fsck will be done.
>>> But afterwards one has less free memory available than normal.
>>> Example:
>>> used mem immediately after login:
>>>   without fsck during boot:  98 MB (this the normal level here)
>>>   with fsck during boot   : 139 MB
>>> So, there is a memory leak of about 41 MB.
>>
>> Please send the output of cat /proc/meminfo (a) before running fsck,
>> (b) after running fsck, and then (c) after running "echo 3 >
>> /proc/sys/vm/drop_caches".
>
> Just tried it out.
> Doing "echo 3 > /proc/sys/vm/drop_caches" solves the problem.

But thinking twice about this leads me to the conclusion that
there still must be something fishy in the system, because
I had read the used mem from the "-/+ buffers/cache" line of the "free -lh" 
command, here an example output:

$ free -lh
              total       used       free     shared    buffers     cached
Mem:          6.9G       1.3G       5.6G        17M        70M       882M
Low:          6.9G       1.3G       5.6G
High:           0B         0B         0B
-/+ buffers/cache:       404M       6.5G
Swap:         8.0G         0B       8.0G

So, it should have already counted-in the cached memory, and IMO it does.
But then it's mysterious why the said discrepancy of 41 MB shows up
if /proc/sys/vm/drop_caches has the default value of 0.