Hi, I was trying to implement the following problem statement from the book *Programming Elixer* in go.
Let's write some code that creates n processes. The first will send a > number to the second. It will increment that number and pass it to the > third. This will continue until we get to the last process, which will pass > the number back to the top level My implementation: https://play.golang.org/p/iI8GqQ08q6 While attempting to do this I realised once the process complete I see the application taking up a large chunk of memory. I was trying to understand why this was happening. Why is go still holding up memory after the computation is done? memleak git:(master) ✗ GODEBUG=gctrace=1 ./memleak 1000000 Alloc = 60 TotalAlloc = 60 Sys = 1700 NumGC = 0 before: go routines 2 result: 1000000 after: go routines 2 Ctrl-C to exit gc 1 @1.300s 4%: 40+96+0.10 ms clock, 322+77/89/123+0.81 ms cpu, 260->260-> 170 MB, 261 MB goal, 8 P Alloc = 184148 TotalAlloc = 260398 Sys = 1137084 NumGC = 1 GC forced gc 2 @126.456s 0%: 0.012+101+0.049 ms clock, 0.10+0/96/118+0.39 ms cpu, 170 ->170->170 MB, 340 MB goal, 8 P scvg0: inuse: 180, idle: 882, sys: 1063, released: 0, consumed: 1063 (MB) GC forced gc 3 @246.577s 0%: 0.011+107+0.051 ms clock, 0.094+0/102/122+0.41 ms cpu, 170->170->170 MB, 340 MB goal, 8 P GC forced scvg1: 882 MB released scvg1: inuse: 180, idle: 882, sys: 1063, released: 882, consumed: 180 (MB) gc 4 @366.708s 0%: 0.016+116+24 ms clock, 0.13+0/111/128+197 ms cpu, 170-> 170->170 MB, 340 MB goal, 8 P GC forced gc 5 @486.868s 0%: 0.012+114+0.063 ms clock, 0.10+0/114/138+0.50 ms cpu, 170 ->170->170 MB, 340 MB goal, 8 P scvg2: 0 MB released scvg2: inuse: 180, idle: 882, sys: 1063, released: 882, consumed: 180 (MB) GC forced gc 6 @607.003s 0%: 0.014+112+0.058 ms clock, 0.11+0/106/125+0.46 ms cpu, 170 ->170->170 MB, 340 MB goal, 8 P GC forced scvg3: inuse: 180, idle: 882, sys: 1063, released: 882, consumed: 180 (MB) gc 7 @727.144s 0%: 0.013+39+0.052 ms clock, 0.10+0/52/228+0.41 ms cpu, 170-> 170->170 MB, 340 MB goal, 8 P GC forced gc 8 @847.203s 0%: 0.012+65+0.060 ms clock, 0.097+0/69/189+0.48 ms cpu, 170 ->170->170 MB, 340 MB goal, 8 P scvg4: inuse: 180, idle: 882, sys: 1063, released: 882, consumed: 180 (MB) memleak git:(master) ✗ top -o mem PID COMMAND %CPU TIME #TH #WQ #PORTS MEM PURG CMPRS PGRP PPID STATE BOOSTS %CPU_ME %CPU_OTHRS UID FAULTS COW MSGSENT MSGRECV SYSBSD SYSMACH 0 kernel_task 5.1 13:52:38 136/8 0 2 1501M- 0B 0B 0 0 running 0[0] 0.00000 0.00000 0 1699585 75 1476697193+ 1255953068+ 0 0 63272 memleak 0.0 00:05.91 11 0 35 1163M 0B 0B 63272 33103 sleeping *0[1] 0.00000 0.00000 501 298605 80 42 20 277052 320101 Also when I change up this implementation to do something different, while still spawning up 1 million goroutines and buffered channels this memory usage drops considerably. Changed code : https://play.golang.org/p/pJ2Y7ENXna memleak git:(master) ✗ GODEBUG=gctrace=1 ./memleak 1000000 Alloc = 61 TotalAlloc = 61 Sys = 1700 NumGC = 0 before: go routines 2 gc 1 @0.000s 0%: 0.056+810+0.030 ms clock, 0.17+0.005/0.070/810+0.092 ms cpu , 7->8->8 MB, 8 MB goal, 8 P buffered: started all go goutines 2 buffered: final count 1000000 after: go routines 2 Alloc = 8198 TotalAlloc = 8205 Sys = 14434 NumGC = 1 Ctrl-C to exit >From what I understand reading and a few comments from the gopher slack, this is because go is not releasing memory back to OS but holds it for a longer in case it needs this, if that makes sense? It would be really helpful, if someone could help me understand this. -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
