Web服务器使用的实际内存。 内存未释放到操作系统

I push a bunch of requests through the web server, and according to Htop / activity monitor on my mac, Virt is 530G, Res is 247Mb.

The memory doesn't seem to be being released to the OS. I tried adding the following for force memory to be returned to OS as a test to no avail:

func freeMem() {
    tick := time.Tick(time.Second * 10)

    for range tick {
        debug.FreeOSMemory()
    }
}

and at the top of main, calling go freeMem(), but this seems to have no effect.

So I tried checking garbage collector is working properly and visualising with dave cheney's gcvis https://github.com/davecheney/gcvis:

Looks like gcvis shows things are working fine and dandy, but htop & activity monitor seem to be v high memory usage.

Do I have anything to worry about? One thing I did notice in gcvis, is that whilst gc.heapinuse goes down to acceptable levels, scvg.released and scvg.sys seem to remain high.