Bug 1348095

We use v3.7.11, replica 2 setup between 2 nodes + 1 dummy node for 
keeping volumes metadata.

We observe huge VSZ (VIRT) usage by glustershd on dummy node:

===
root     15109  0.0 13.7 76552820 535272 ?     Ssl  тра26   2:11 
/usr/sbin/glusterfs -s localhost --volfile-id gluster/glustershd -p 
/var/lib/glusterd/glustershd/run/glustershd.pid -l 
/var/log/glusterfs/glustershd.log -S 
/var/run/gluster/7848e17764dd4ba80f4623aecb91b07a.socket --xlator-option 
*replicate*.node-uuid=80bc95e1-2027-4a96-bb66-d9c8ade624d7
===

that is ~73G. RSS seems to be OK (~522M). Here is the statedump of 
glustershd process: https://gist.github.com/d2cfa25251136512580220fcdb8a6ce6

Also, here is sum of sizes, presented in statedump:

===
# cat /var/run/gluster/glusterdump.15109.dump.1465200139 | awk -F '=' 
'BEGIN {sum=0} /^size=/ {sum+=$2} END {print sum}'
353276406
===

That is ~337 MiB.

Also, I see lots of entries in pmap output:

===
00007ef9ff8f3000      4K -----   [ anon ]
00007ef9ff8f4000   8192K rw---   [ anon ]
00007efa000f4000      4K -----   [ anon ]
00007efa000f5000   8192K rw---   [ anon ]
===

If I sum them, I get the following:

===
# pmap 15109 | grep '[ anon ]' | grep 8192K | wc -l
9261
$ echo "9261*(8192+4)" | bc
75903156
===

Which is something like 70G+ I have got in VIRT.

Also, here are VIRT values from 2 replica nodes:

===
root     24659  0.0  0.3 5645836 451796 ?      Ssl  тра24   3:28 
/usr/sbin/glusterfs -s localhost --volfile-id gluster/glustershd -p 
/var/lib/glusterd/glustershd/run/glustershd.pid -l 
/var/log/glusterfs/glustershd.log -S 
/var/run/gluster/44ec3f29003eccedf894865107d5db90.socket --xlator-option 
*replicate*.node-uuid=a19afcc2-e26c-43ce-bca6-d27dc1713e87
root     18312  0.0  0.3 6137500 477472 ?      Ssl  тра19   6:37 
/usr/sbin/glusterfs -s localhost --volfile-id gluster/glustershd -p 
/var/lib/glusterd/glustershd/run/glustershd.pid -l 
/var/log/glusterfs/glustershd.log -S 
/var/run/gluster/1670a3abbd1eea968126eb6f5be20322.socket --xlator-option 
*replicate*.node-uuid=52dca21b-c81c-48b5-9de2-1ed37987fbc2
===

Those are 5 to 6G, which is much less than dummy node has, but still 
look too big for us.

Digging into logs showed that there are lots of reconnections to bricks (due to failing network). VSZ and RSS grows on each reconnection, VSZ by ~24M, RSS by ~500K.

I've taken 5 statedumps with 30 mins between each statedump. Also, 
before taking the statedump, I've recorded memory usage.

Memory consumption:

1. root      1010  0.0  9.6 7538188 374864 ?      Ssl  чер07   0:16 
/usr/sbin/glusterfs -s localhost --volfile-id gluster/glustershd -p 
/var/lib/glusterd/glustershd/run/glustershd.pid -l 
/var/log/glusterfs/glustershd.log -S 
/var/run/gluster/7848e17764dd4ba80f4623aecb91b07a.socket --xlator-option 
*replicate*.node-uuid=80bc95e1-2027-4a96-bb66-d9c8ade624d7
2. root      1010  0.0  9.6 7825048 375312 ?      Ssl  чер07   0:16 
/usr/sbin/glusterfs -s localhost --volfile-id gluster/glustershd -p 
/var/lib/glusterd/glustershd/run/glustershd.pid -l 
/var/log/glusterfs/glustershd.log -S 
/var/run/gluster/7848e17764dd4ba80f4623aecb91b07a.socket --xlator-option 
*replicate*.node-uuid=80bc95e1-2027-4a96-bb66-d9c8ade624d7
3. root      1010  0.0  9.6 7825048 375312 ?      Ssl  чер07   0:17 
/usr/sbin/glusterfs -s localhost --volfile-id gluster/glustershd -p 
/var/lib/glusterd/glustershd/run/glustershd.pid -l 
/var/log/glusterfs/glustershd.log -S 
/var/run/gluster/7848e17764dd4ba80f4623aecb91b07a.socket --xlator-option 
*replicate*.node-uuid=80bc95e1-2027-4a96-bb66-d9c8ade624d7
4. root      1010  0.0  9.6 8202064 375892 ?      Ssl  чер07   0:17 
/usr/sbin/glusterfs -s localhost --volfile-id gluster/glustershd -p 
/var/lib/glusterd/glustershd/run/glustershd.pid -l 
/var/log/glusterfs/glustershd.log -S 
/var/run/gluster/7848e17764dd4ba80f4623aecb91b07a.socket --xlator-option 
*replicate*.node-uuid=80bc95e1-2027-4a96-bb66-d9c8ade624d7
5. root      1010  0.0  9.6 8316808 376084 ?      Ssl  чер07   0:17 
/usr/sbin/glusterfs -s localhost --volfile-id gluster/glustershd -p 
/var/lib/glusterd/glustershd/run/glustershd.pid -l 
/var/log/glusterfs/glustershd.log -S 
/var/run/gluster/7848e17764dd4ba80f4623aecb91b07a.socket --xlator-option 
*replicate*.node-uuid=80bc95e1-2027-4a96-bb66-d9c8ade624d7

As you may see VIRT constantly grows (except for one measurements), and 
RSS grows as well, although its increase is considerably smaller.

Now lets take a look at statedumps:

1. https://gist.github.com/3fa121c7531d05b210b84d9db763f359
2. https://gist.github.com/87f48b8ac8378262b84d448765730fd9
3. https://gist.github.com/f8780014d8430d67687c70cfd1df9c5c
4. https://gist.github.com/916ac788f806328bad9de5311ce319d7
5. https://gist.github.com/8ba5dbf27d2cc61c04ca954d7fb0a7fd

I'd go with comparing first statedump with last one, and here is diff 
output: https://gist.github.com/e94e7f17fe8b3688c6a92f49cbc15193

I see numbers changing, but now cannot conclude what is meaningful and 
what is meaningless.