RSS usage higher on newer fedora releases higher for user-applications compared to 3.11.10-301.fc20.x86_64 release, what might be the reason?

[Anand Babu]

So, We were trying to move to Fedora 33  from Centos7  for our jvm and then we  found the
memory consumption to be higher than Centos7. 

we did the following:

Step :1 Narrow the problem with a simple c-code

#include<unistd.h>

int main()

{
pause();
return 0;
}

Running this c-program  on Fedora 33 yields 660 KB .  While on centos7, it only takes  348
KB, 

Step 2: 

Narrow down the kernel versions . 

So, we tried testing different fedora VMs that we had and one of the VMs was running
fedora 20. We were able to boot 

1. kernel-3.11.10-301.fc20.x86_64 

2. kernel-3.17.4-200.fc20.x86_64 



With kernel-3.11, pmap tells the RSS was only 388KB . Screenshot of pmap here:
(https://ibb.co/D5zTXvs) 

while on kernel-3.17 its 920KB (https://ibb.co/vLByKkD) . 

From the pmap mappings, we see both the binaries are using the same glibc and ld.so etc. 
So, this seems like nothing has changed on the user-land while the RSS measurement has
more than doubled. 

Could somehow have an idea on what else could explain the reason for his memory increase?
This seems like something has changed from the kernel side in terms of how RSS was
measured or the defaults have changed? 


Regards,
-Anand

[Jonathan Billings]

On Tue, Jul 20, 2021 at 08:23:33AM -0000, Anand Babu wrote:
>  
>  So, We were trying to move to Fedora 33  from Centos7  for our jvm and then we  found the
> memory consumption to be higher than Centos7.  
Did the suggestion you got when you posted this on the CentOS list
help?

https://lists.centos.org/pipermail/centos/2021-July/354153.html

-- 
Jonathan Billings <billings(a)negate.org&gt;

[Anand Babu]

Thanks for taking the time to comment about the interest in our problem.

I had "digest mode" setup for the email preference  and i could not reply
to that particular message to the whole group(though i replied to the
"digest email" and i could not see that on the mailing list .

I responded to the person(Leon) who made that helpful suggestion  directly
that it dint change the pmap output and i could still see the original
problem.



Now,  thanks to your question, here is the full output of trying that
suggestion:

1. Before implementing the suggestion:

* cat /sys/kernel/mm/transparent_hugepage/enabledalways [madvise] never*

2. Implemented the suggestion and verified as below:

*[root@fedora-20-64 ~]#  cat
/sys/kernel/mm/transparent_hugepage/enabledalways madvise [never]*

3. Still, i see the following pmap output:

[root@fedora-20-64 ~]#
* pmap -X $(pidof test)1577:   ./test*
         Address Perm   Offset Device Inode Size  *Rss* Pss Referenced
Anonymous Swap Locked Mapping
        00400000 r-xp 00000000  00:21 88738    4    4   4          4
  0    0      0 test
        00600000 r--p 00000000  00:21 88738    4    4   4          4
  4    0      0 test
        00601000 rw-p 00001000  00:21 88738    4    4   4          4
  4    0      0 test
    7f3fe3f88000 r-xp 00000000  fd:00  1751 1744  796  12        796
  0    0      0 libc-2.18.so
    7f3fe413c000 ---p 001b4000  fd:00  1751 2044    0   0          0
  0    0      0 libc-2.18.so
    7f3fe433b000 r--p 001b3000  fd:00  1751   16   16  16         16
 16    0      0 libc-2.18.so
    7f3fe433f000 rw-p 001b7000  fd:00  1751    8    8   8          8
  8    0      0 libc-2.18.so
    7f3fe4341000 rw-p 00000000  00:00     0   20   12  12         12
 12    0      0
    7f3fe4346000 r-xp 00000000  fd:00  1257  128  128   1        128
  0    0      0 ld-2.18.so
    7f3fe454e000 rw-p 00000000  00:00     0   12   12  12         12
 12    0      0
    7f3fe4564000 rw-p 00000000  00:00     0    4    4   4          4
  4    0      0
    7f3fe4565000 r--p 0001f000  fd:00  1257    4    4   4          4
  4    0      0 ld-2.18.so
    7f3fe4566000 rw-p 00020000  fd:00  1257    4    4   4          4
  4    0      0 ld-2.18.so
    7f3fe4567000 rw-p 00000000  00:00     0    4    4   4          4
  4    0      0
    7fffeded0000 rw-p 00000000  00:00     0  136    8   8          8
  8    0      0 [stack]
    7fffedf42000 r--p 00000000  00:00     0    8    0   0          0
  0    0      0 [vvar]
    7fffedf44000 r-xp 00000000  00:00     0    8    4   0          4
  0    0      0 [vdso]
ffffffffff600000 r-xp 00000000  00:00     0    4    0   0          0
  0    0      0 [vsyscall]
                                            ==== ==== === ==========
========= ==== ======
                                            4156 *1012*  97       1012
   80    0      0 KB


Enabling that option seemed to have increased the RSS output by about 80KB
to 1012(though we do see some noise across different runs to be honest ).

We will be glad to hear any further inputs on this issue.


Regards,
-Anand

On Tue, Jul 20, 2021 at 3:45 PM Jonathan Billings <billings(a)negate.org&gt;
wrote:

>  On Tue, Jul 20, 2021 at 08:23:33AM -0000, Anand Babu wrote:
>  >
>  >
>  > So, We were trying to move to Fedora 33  from Centos7  for our jvm and
>  then we  found the memory consumption to be higher than Centos7.
>
>  Did the suggestion you got when you posted this on the CentOS list
>  help?
>
>  https://lists.centos.org/pipermail/centos/2021-July/354153.html
>
>  --
>  Jonathan Billings <billings(a)negate.org&gt;
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[Patrick O'Callaghan]

On Tue, 2021-07-20 at 16:23 +0200, Anand Babu wrote:
>  I had "digest mode" setup for the email preference  and i
> could not
>  reply
>  to that particular message to the whole group(though i replied to the
>  "digest email" and i could not see that on the mailing list .
>   
Just as an aside, most email clients support replying to a specific
message within a digest (rather than to the whole digest), e.g. in
Evolution right-click on the message to select the option.

On the whole however, digests are a relic of the days of UUCP mail and
are better avoided. One list I moderate disabled them several years ago
and we've had no complaints.

poc