Memory profiling

[josecelano]

Relates to: #825

Recently I've been increasing the server where we host the live demo because the server was running out of memory.

I've also been discussing whether it makes sense to limit the memory consumed by the application.

In parallel, it would be good to know which parts of the applications are the greatest memory consumers in the applications.

Likely the torrent repository is the data structure that consumes a great percentage of the application's total memory consumption, but there could also be other parts like:

• Threads (especially if we have deadlocks that keep threads around for too long)
• Responses

I don't know how to do memory profiling, but I would start with something simple like calculating the size and number of the structs we think are the most consuming and comparing it with the total memory used by the application.

@mickvandijke was doing memory consumption calculations in this PR for the torrent repository.

@Power2All suggested using pmap. This is the current output in the live demo:

pmap 3550131
3550131:   /usr/bin/torrust-tracker
000056238845c000    568K r---- torrust-tracker
00005623884ea000   8284K r-x-- torrust-tracker
0000562388d01000   2712K r---- torrust-tracker
0000562388fa7000    380K r---- torrust-tracker
0000562389006000     16K rw--- torrust-tracker
000056238900a000      4K rw---   [ anon ]
0000562389a36000    132K rw---   [ anon ]
00007f18c0000000  10976K rw---   [ anon ]
00007f18c0ab8000  54560K -----   [ anon ]
00007f18c8000000  65232K rw---   [ anon ]
00007f18cbfb4000    304K -----   [ anon ]
00007f18d0000000  65532K rw---   [ anon ]
00007f18d3fff000      4K -----   [ anon ]
00007f18d4000000  65536K rw---   [ anon ]
00007f18d8000000  65536K rw---   [ anon ]
00007f18dc000000  65536K rw---   [ anon ]
00007f18e0000000  65532K rw---   [ anon ]
00007f18e3fff000      4K -----   [ anon ]
00007f18e4000000  65532K rw---   [ anon ]
00007f18e7fff000      4K -----   [ anon ]
00007f18e8000000  65536K rw---   [ anon ]
00007f18f0000000  65536K rw---   [ anon ]
00007f18f8000000  65536K rw---   [ anon ]
00007f18fc000000  65536K rw---   [ anon ]
00007f1900000000  65536K rw---   [ anon ]
00007f1904000000  65532K rw---   [ anon ]
00007f1907fff000      4K -----   [ anon ]
00007f1908000000  65536K rw---   [ anon ]
00007f190c000000  65536K rw---   [ anon ]
00007f1910000000  65536K rw---   [ anon ]
00007f1914000000  65536K rw---   [ anon ]
00007f1918000000  65536K rw---   [ anon ]
00007f191c000000  65536K rw---   [ anon ]
00007f1920000000  65536K rw---   [ anon ]
00007f1928000000  65536K rw---   [ anon ]
00007f192c000000  65536K rw---   [ anon ]
00007f1930000000  65536K rw---   [ anon ]
00007f1934000000  65536K rw---   [ anon ]
00007f1938000000    496K rw---   [ anon ]
00007f193807c000  65040K -----   [ anon ]
00007f193c000000    524K rw---   [ anon ]
00007f193c083000  65012K -----   [ anon ]
00007f1940000000  65532K rw---   [ anon ]
00007f1943fff000      4K -----   [ anon ]
00007f1944000000    496K rw---   [ anon ]
00007f194407c000  65040K -----   [ anon ]
00007f1948000000  65536K rw---   [ anon ]
00007f194d216000      4K -----   [ anon ]
00007f194d217000      8K rw---   [ anon ]
00007f194d219000      4K -----   [ anon ]
00007f194d21a000      8K rw---   [ anon ]
00007f194d21c000      4K -----   [ anon ]
00007f194d21d000   2048K rw---   [ anon ]
00007f194d41d000      4K -----   [ anon ]
00007f194d41e000      8K rw---   [ anon ]
00007f194d420000      4K -----   [ anon ]
00007f194d421000   2048K rw---   [ anon ]
00007f194d621000      4K -----   [ anon ]
00007f194d622000   2048K rw---   [ anon ]
00007f194d822000      4K -----   [ anon ]
00007f194d823000      8K rw---   [ anon ]
00007f194d825000      4K -----   [ anon ]
00007f194d826000      8K rw---   [ anon ]
00007f194d828000      4K -----   [ anon ]
00007f194d829000   2048K rw---   [ anon ]
00007f194da29000      4K -----   [ anon ]
00007f194da2a000   2048K rw---   [ anon ]
00007f194dc2a000      4K -----   [ anon ]
00007f194dc2b000     20K rw---   [ anon ]
00007f194dc30000    152K r---- libc.so.6
00007f194dc56000   1364K r-x-- libc.so.6
00007f194ddab000    332K r---- libc.so.6
00007f194ddfe000     16K r---- libc.so.6
00007f194de02000      8K rw--- libc.so.6
00007f194de04000     60K rw---   [ anon ]
00007f194de13000     64K r---- libm.so.6
00007f194de23000    460K r-x-- libm.so.6
00007f194de96000    360K r---- libm.so.6
00007f194def0000      4K r---- libm.so.6
00007f194def1000      4K rw--- libm.so.6
00007f194def2000     12K r---- libgcc_s.so.1
00007f194def5000     92K r-x-- libgcc_s.so.1
00007f194df0c000     16K r---- libgcc_s.so.1
00007f194df10000      4K r---- libgcc_s.so.1
00007f194df11000      4K rw--- libgcc_s.so.1
00007f194df12000    788K r---- libcrypto.so.3
00007f194dfd7000   2532K r-x-- libcrypto.so.3
00007f194e250000    884K r---- libcrypto.so.3
00007f194e32d000    388K r---- libcrypto.so.3
00007f194e38e000     12K rw--- libcrypto.so.3
00007f194e391000     12K rw---   [ anon ]
00007f194e394000    124K r---- libssl.so.3
00007f194e3b3000    376K r-x-- libssl.so.3
00007f194e411000    124K r---- libssl.so.3
00007f194e430000     40K r---- libssl.so.3
00007f194e43a000     16K rw--- libssl.so.3
00007f194e43e000     12K r---- libz.so.1
00007f194e441000     76K r-x-- libz.so.1
00007f194e454000     28K r---- libz.so.1
00007f194e45b000      4K r---- libz.so.1
00007f194e45c000      4K rw--- libz.so.1
00007f194e45d000      8K rw---   [ anon ]
00007f194e45f000      4K r---- ld-linux-x86-64.so.2
00007f194e460000    148K r-x-- ld-linux-x86-64.so.2
00007f194e485000     40K r---- ld-linux-x86-64.so.2
00007f194e48f000      8K r---- ld-linux-x86-64.so.2
00007f194e491000      8K rw--- ld-linux-x86-64.so.2
00007ffdbfef9000    132K rw---   [ stack ]
00007ffdbff62000     16K r----   [ anon ]
00007ffdbff66000      8K r-x--   [ anon ]
ffffffffff600000      4K --x--   [ anon ]
 total          1997268K

And for top command:

top - 16:15:12 up 4 days,  9:13,  1 user,  load average: 4.32, 3.34, 3.26
Tasks: 238 total,   1 running, 131 sleeping,   0 stopped, 106 zombie
%Cpu(s): 13.3 us, 13.2 sy,  0.0 ni, 28.1 id, 18.2 wa,  0.0 hi,  3.9 si, 23.3 st
MiB Mem :   3911.9 total,    129.3 free,   2302.8 used,   1479.9 buff/cache
MiB Swap:      0.0 total,      0.0 free,      0.0 used.   1355.2 avail Mem

    PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
3550131 torrust   20   0 2062800   1.6g  10032 S  21.9  43.1 446:22.78 torrust-tracker