Add zswap metrics: bytes_used and compression_efficiency

[divikchotani-oss]

This commit adds tracking for memory/zswap_bytes_used and memory/zswap_compression_efficiency via procfs.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: divikchotani-oss / name: Divik Chotani (368a56c)

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[kubernetes-prow]

Hi @divikchotani-oss. Thanks for your PR.

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[AnishShah]

/ok-to-test

[ajaysundark]

/test pull-npd-e2e-test

[AnishShah]

/assign @wangzhen127

[AnishShah]

/lgtm

[wangzhen127]

Can you add some unit test?

[wangzhen127]

and can you squash the commits after the update?

[divikchotani-oss]

I added unit tests for zswap to the commit and squashed it all into one commit, thanks

[DigitalVeer]

Thanks for this update! Can we please update the systemstatsmonitor documentation as well.

[DigitalVeer]

Is this metric registered and/or launched? I cannot find any documentation and some issues came up when testing locally.

1. CreateTimeSeries rejected on both spellings:

control  guest/memory/percent_used            → {}  (accepted)
PR type  guest/memory/zswap/bytes_used        → 400 INVALID_ARGUMENT "unknown metric type"
flat     guest/memory/zswap_bytes_used        → 400 INVALID_ARGUMENT "unknown metric type"

2. Not in the API descriptors:

$ GET /v3/projects/…/metricDescriptors?filter=starts_with("compute.googleapis.com/guest")
-- No match for zswap

3. Running on stackdriver fails on every export:

… metric.type="compute.googleapis.com/guest/memory/zswap/compression_efficiency" … unknown metric type
… metric.type="compute.googleapis.com/guest/memory/zswap/bytes_used" … unknown metric type

[divikchotani-oss]

Hi, thanks for the catch! I updated the documentation, the reason for the error is because the metric descriptors have not yet been registered in the backend, once that happens, the errors should be resolved.

[wangzhen127]

/lgtm

[kubernetes-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: AnishShah, divikchotani-oss, wangzhen127

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