docker_logger: reorder imports to save memory #14875
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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 404d2d4. This changeset restores the ordering. A follow-up heap dump shows this saves ~2MB of unshared RSS per docker_logger process.
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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 404d2d4. This changeset restores the ordering. A follow-up heap dump shows this saves ~2MB of unshared RSS per docker_logger process.
tgross
added a commit
that referenced
this pull request
Oct 11, 2022
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 404d2d4. This changeset restores the ordering. A follow-up heap dump shows this saves ~2MB of unshared RSS per docker_logger process. Co-authored-by: Tim Gross <tgross@hashicorp.com>
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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_Cleanin 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.Argsto 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 404d2d4. This changeset restores the ordering. A follow-up heap dump shows this saves ~2MB of unshared RSS per docker_logger process.