[erlang-questions] How to dig why get_tcp/port allocate so much binary memory?

叶少波 <>
Thu Sep 22 11:41:14 CEST 2016


Hi experts,


I wrote a server that accepts TCP connections. The listen socket starts with the options below:
  -define(TCP_OPTS, [
    binary,
    {backlog, 256},
    {packet, 0},
    {active, false},
    {reuseaddr, true},
    {nodelay, false},
    {delay_send, true},
    {keepalive, true},
    {send_timeout, 60000},
    {exit_on_close, true}
]).

On the server node every new connection will spawn a new gen_server to handle it.


And  then I spawn 5000 gen_servers on another erlang node(I call it Client node), every gen_server will connect to the server via TCP.


It is a really simple case.


After setup 5000 connections I found the binary memory on server node was used up to 17G;
and the binary memory on the Client node was 42M.  It is a huge difference.


Then I rebooted  the erlang node with "+Mim true"  and "+Mis true"; after re-setup 5000 connections again, I used 
instrument:memory_status(types) to check the memory status, I found the dry_binary allocated 17G memory:
[{drv_binary,[{sizes,1844114912,1844116842,1844116842},
              {blocks,5227,5724,5724}]},
 {code,[{sizes,39944997,39955374,39955374},
        {blocks,1321,1321,1321}]},
 {heap,[{sizes,28000216,78942872,78942872},
        {blocks,5263,5267,5267}]},
 {old_heap,[{sizes,21132056,72481264,72481264},
            {blocks,2940,4736,4736}]},
 {binary,[{sizes,17908918,21738516,21738516},
          {blocks,25087,35039,35039}]},
 {proc_tab,[{sizes,12582975,12582975,12582975},
            {blocks,1,1,1}]},
 {export_entry,[{sizes,7108992,7108992,7108992},
                {blocks,40392,40392,40392}]},
 {db_term,[{sizes,6930120,6930200,6930200},
           {blocks,13149,13150,13150}]},
 {port_tab,[{sizes,6291519,6291519,6291519},{blocks,1,1,1}]},
 {proc,[{sizes,4211200,4212800,4212800},
        {blocks,5264,5266,5266}]},
 {port,[{sizes,3392108,3393432,3393432},
        {blocks,5101,5103,5103}]},

.......


My question is : How can I decrease the drv_binary memory? What parameter caused the server used so much memory?


Thanks,
BRs/Michael
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