From 5e225a4ff57ce26fcc628903c8dcd19a6fd1eea5 Mon Sep 17 00:00:00 2001 From: Tim Gross Date: Tue, 11 Oct 2022 13:23:03 -0400 Subject: [PATCH] docker_logger: reorder imports to save memory (#14875) Nomad runs one logmon process and also one docker_logger process for each running allocation. A naive look at memory usage shows 10-30 MB of RSS, but a closer look shows that most of this memory (ex. all but ~2MB for logmon) is shared (`Shared_Clean` in Linux pmap). But a heap dump of docker_logger shows that it currently has an extra ~2500 KiB of heap (anonymously-mapped unshared memory) used for init blocks coming from the agent code (ex. mostly regexes from go-version, structs, and the Consul SDK). The packages for running logmon, docker_logger, and executor have an init block that parses `os.Args` to drop into their own logic, which prevents them from loading all the rest of the agent code and saves on memory, so this was unexpected. It looks like we accidentally reordered the imports in main to undo some of the work originally done in 404d2d4c98f1df930be1ae9852fe6e6ae8c1517e. This changeset restores the ordering. A follow-up heap dump shows this saves ~2MB of unshared RSS per docker_logger process. --- main.go | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/main.go b/main.go index ee599656c0c5..baeefc107549 100644 --- a/main.go +++ b/main.go @@ -12,11 +12,12 @@ import ( // These packages have init() funcs which check os.Args and drop directly // into their command logic. This is because they are run as separate // processes along side of a task. By early importing them we can avoid - // additional code being imported and thus reserving memory + // additional code being imported and thus reserving memory. _ "github.com/hashicorp/nomad/client/logmon" _ "github.com/hashicorp/nomad/drivers/docker/docklog" _ "github.com/hashicorp/nomad/drivers/shared/executor" + // Don't move any other code imports above the import block above! "github.com/hashicorp/nomad/command" "github.com/hashicorp/nomad/version" "github.com/mitchellh/cli"