fix(noise): only change hugepage state if needed

[noelmcloughlin]

PR progress checklist (to be filled in by reviewers)

• Changes to documentation are appropriate (or tick if not required)
• Changes to tests are appropriate (or tick if not required)
• Reviews completed

---

What type of PR is this?

Primary type

• [build] Changes related to the build system
• [chore] Changes to the build process or auxiliary tools and libraries such as documentation generation
• [ci] Changes to the continuous integration configuration
• [feat] A new feature
• [fix] A bug fix
• [perf] A code change that improves performance
• [refactor] A code change that neither fixes a bug nor adds a feature
• [revert] A change used to revert a previous commit
• [style] Changes that do not affect the meaning of the code (white-space, formatting, missing semi-colons, etc.)

Secondary type

• [docs] Documentation changes
• [test] Adding missing or correcting existing tests

Does this PR introduce a BREAKING CHANGE?

No.

Related issues and/or pull requests

#89

Describe the changes you're proposing

Enable hugepages only when needed, not everytime

Pillar / config required to test the proposed changes

Debug log showing how the proposed changes work

Documentation checklist

• Updated the README (e.g. Available states).
• Updated pillar.example.

Testing checklist

• Included in Kitchen (i.e. under state_top).
• Covered by new/existing tests (e.g. InSpec, Serverspec, etc.).
• Updated the relevant test pillar.

Additional context

[iaingeorgeson]

Thanks for taking a look at this.

Unfortunately, I don't think this commit solves the problem. This file is on sysfs, The command changes the state rather than creating it, and the current state is marked in its contents with square brackets:

always madvise [never]

So the test would be something like:

- unless: grep -q '[never]' /sys/kernel/mm/transparent_hugepage/enabled

[noelmcloughlin]

i checked https://redis.io/topics/latency and you are correct.
We can assume Redis formula should enforce never.
I'll update the commit.

The ideal solution is probably to create a service file (https://docs.mongodb.com/manual/tutorial/transparent-huge-pages) but you could open separate issue for that and someone will get around to it sometime.

[noelmcloughlin]

$ echo never >/tmp/dave
$ grep -ir '^never' /tmp/dave
never
$ echo $?
0
$ echo always >/tmp/dave
$ grep -ir '^never' /tmp/dave
$ echo $?
1

[iaingeorgeson]

# echo never >/sys/kernel/mm/transparent_hugepage/enabled
# grep -ir '^never' /sys/kernel/mm/transparent_hugepage/enabled
# echo $?
1
# echo always >/sys/kernel/mm/transparent_hugepage/enabled
# grep -ir '^never' /sys/kernel/mm/transparent_hugepage/enabled
# echo $?
1

[saltstack-formulas-travis]

🎉 This PR is included in version 0.27.1 🎉

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