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Don't use CachingObject if the number of watchers is small #84043

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merged 1 commit into from
Oct 18, 2019
Merged

Don't use CachingObject if the number of watchers is small #84043

merged 1 commit into from
Oct 18, 2019

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wojtek-t
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@wojtek-t wojtek-t commented Oct 17, 2019 •
edited

The gain from using CachingObject is huge when there is huge number of watchers (e.g. 5000 kube-proxies, watching all Endpoints objects).
However, if the number of watchers is very small (say 1), creation of the CachingObject itself is unnecessary cost (it results in a bunch of memory allocations):

  • if there are 0 watchers - it is complete waste
  • if there is 1 watcher - gain from caching is 0, so we unnecessary copy stuff to create CachingObject
  • if there are 2 watchers - additional copy is roughly amortized by saved serialization
    So only with 3+ watchers the gain starts to be visible.

This PR is changing the logic to use CachingObject only in this case.

The gain in large clusters isn't huge - seem to be ~1-2%, but probably still worth given how small this change is.

@wojtek-t wojtek-t self-assigned this Oct 17, 2019
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@wojtek-t: Adding the "do-not-merge/release-note-label-needed" label because no release-note block was detected, please follow our release note process to remove it.

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@k8s-ci-robot k8s-ci-robot added size/L Denotes a PR that changes 100-499 lines, ignoring generated files. do-not-merge/release-note-label-needed Indicates that a PR should not merge because it's missing one of the release note labels. cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. needs-kind Indicates a PR lacks a `kind/foo` label and requires one. needs-sig Indicates an issue or PR lacks a `sig/foo` label and requires one. needs-priority Indicates a PR lacks a `priority/foo` label and requires one. labels Oct 17, 2019
@wojtek-t wojtek-t changed the title Don't use CachingObject if the number of watchers is small [WIP] Don't use CachingObject if the number of watchers is small Oct 17, 2019
@k8s-ci-robot k8s-ci-robot added the do-not-merge/work-in-progress Indicates that a PR should not merge because it is a work in progress. label Oct 17, 2019
@k8s-ci-robot k8s-ci-robot added approved Indicates a PR has been approved by an approver from all required OWNERS files. area/apiserver sig/api-machinery Categorizes an issue or PR as relevant to SIG API Machinery. and removed needs-sig Indicates an issue or PR lacks a `sig/foo` label and requires one. labels Oct 17, 2019
@wojtek-t wojtek-t added release-note-none Denotes a PR that doesn't merit a release note. kind/feature Categorizes issue or PR as related to a new feature. priority/important-longterm Important over the long term, but may not be staffed and/or may need multiple releases to complete. and removed do-not-merge/release-note-label-needed Indicates that a PR should not merge because it's missing one of the release note labels. needs-kind Indicates a PR lacks a `kind/foo` label and requires one. needs-priority Indicates a PR lacks a `priority/foo` label and requires one. labels Oct 17, 2019
@wojtek-t wojtek-t changed the title [WIP] Don't use CachingObject if the number of watchers is small Don't use CachingObject if the number of watchers is small Oct 17, 2019
@k8s-ci-robot k8s-ci-robot removed the do-not-merge/work-in-progress Indicates that a PR should not merge because it is a work in progress. label Oct 17, 2019
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@wojtek-t: Adding the "do-not-merge/release-note-label-needed" label because no release-note block was detected, please follow our release note process to remove it.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

@k8s-ci-robot k8s-ci-robot added do-not-merge/release-note-label-needed Indicates that a PR should not merge because it's missing one of the release note labels. and removed release-note-none Denotes a PR that doesn't merit a release note. labels Oct 17, 2019
@wojtek-t wojtek-t assigned liggitt and unassigned wojtek-t Oct 17, 2019
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/retest

liggitt
liggitt reviewed Oct 17, 2019
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staging/src/k8s.io/apiserver/pkg/storage/cacher/cacher_whitebox_test.go Outdated
}

func TestCachingObjects(t *testing.T) {
testCachingObjects(t, 1)
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nit, call these inside subtests so if they fail we know which one it failed on

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done (hopefully that's what you meant)

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liggitt commented Oct 17, 2019

one nit, lgtm otherwise. would be good to get updated numbers on the performance impact of this change before merge

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one nit, lgtm otherwise. would be good to get updated numbers on the performance impact of this change before merge

Update the PR description:
The gain in large clusters isn't huge - seem to be ~1-2%, but probably still worth given how small this change is.

@liggitt - PTAL

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liggitt commented Oct 17, 2019

The gain in large clusters isn't huge - seem to be ~1-2%, but probably still worth given how small this change is.

that's fine, I mostly wanted numbers to prove this was actually an improvement and there were no unexpected downsides

/lgtm
/approve

@k8s-ci-robot k8s-ci-robot added the lgtm "Looks good to me", indicates that a PR is ready to be merged. label Oct 17, 2019
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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: liggitt, wojtek-t

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@wojtek-t wojtek-t added release-note-none Denotes a PR that doesn't merit a release note. and removed do-not-merge/release-note-label-needed Indicates that a PR should not merge because it's missing one of the release note labels. labels Oct 17, 2019
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/retest
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Review the full test history for this PR.

Silence the bot with an /lgtm cancel or /hold comment for consistent failures.

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/cc @apelisse @jennybuckley

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@k8s-ci-robot k8s-ci-robot merged commit f9acca8 into kubernetes:master Oct 18, 2019
@k8s-ci-robot k8s-ci-robot added this to the v1.17 milestone Oct 18, 2019
@wojtek-t wojtek-t mentioned this pull request Oct 23, 2019
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@wojtek-t wojtek-t deleted the tweak_serialize_object_once branch December 18, 2019 08:27
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