crypto/tls: outBuf of Conn costs too much memory for large number of idle connections

[cch123]

What version of Go are you using (go version)?

$ go version
1.13

Does this issue reproduce with the latest release?

yes

What operating system and processor architecture are you using (go env)?

go env Output

$ go env

What did you do?

We are opening TLS on our online mesh project, which runs in a memory-limited situation. Currently, the TLS costs too much memory in some special apps which have about 100,000 connections

It can be calculated easily: 100,000 * max size of tlsConn.outBuf(16KB + some extra bytes) ≈ 1.6 GB(after go 1.12,), which can cause the process to OOM.

Most of the connections are idle, but still, use much memory because of this outBuf

What did you expect to see?

Don't use so much memory for massive idle tls connections

What did you see instead?

the process is killed by os because of OOM

[gopherbot]

Change https://golang.org/cl/263277 mentions this issue: crypto/tls: reuse the tls Conn's outBuf to reduce memory cost on large number of tls connections

[cagedmantis]

/cc @FiloSottile

[taoyuanyuan]

#28654

[gopherbot]

Change https://golang.org/cl/267957 mentions this issue: crypto/tls: pool Conn's outBuf to reduce memory cost of idle connections