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Merge pull request #53720 from shyamjvs/test-kubemark

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Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

Optimize random string generator to avoid multiple locks & use bit-masking

Ref https://github.com/kubernetes/kubernetes/issues/53327

We recently started seeing a 50% decrease in scheduling throughput (for e.g in kubemark-500 scale job) and turns out https://github.com/kubernetes/kubernetes/pull/53135 introduced it.
The reason is [this call](2caae38d32/plugin/pkg/scheduler/algorithm/predicates/predicates.go (L272)) to create a random 32-length string.
From the code of the `rand` utility (which is being heavily used throughout the system for randomizing object names), I noticed following performance issues:
- to create an n-length string, we are making n calls to `rand.Intn()` each of which does a lock+unlock operation on the RNG.. while just 1 lock+unlock operation is enough for all
- we're choosing one character (from an alphabet of 27 chars) per each random integer.. while we can select 10 characters using a single int63 (by masking and bit-shifting) as 1 character uses just 5 bits of randomness
- the character set is defined as a global slice (mutable), so the compiler needs to fetch length of the slice on each invocation to `len()` (we're making n of those).. while we can just use a const string (immutable) which will make len directly available as a cached constant (yes, go does it!)

This PR is making the above fixes. I'll try to add some benchmarking to measure the difference (as @wojtek-t suggested).

/cc @kubernetes/sig-scalability-misc @kubernetes/sig-scheduling-bugs @kubernetes/sig-api-machinery-misc @wojtek-t @smarterclayton
This commit is contained in:
Kubernetes Submit Queue
2017-10-13 06:11:09 -07:00
committed by GitHub
parent cc49b34d29 0185e55889
commit f1d9962fec
3 changed files with 54 additions and 16 deletions
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16
pkg/controller/serviceaccount/tokens_controller_test.go
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@@ -73,7 +73,7 @@ func tokenSecretReferences() []v1.ObjectReference {
// addTokenSecretReference adds a reference to the ServiceAccountToken that will be created
func addTokenSecretReference(refs []v1.ObjectReference) []v1.ObjectReference {
return addNamedTokenSecretReference(refs, "default-token-stdpg")
return addNamedTokenSecretReference(refs, "default-token-xn8fg")
}
// addNamedTokenSecretReference adds a reference to the named ServiceAccountToken
@@ -118,9 +118,9 @@ func opaqueSecret() *v1.Secret {
}
// createdTokenSecret returns the ServiceAccountToken secret posted when creating a new token secret.
// Named "default-token-stdpg", since that is the first generated name after rand.Seed(1)
// Named "default-token-xn8fg", since that is the first generated name after rand.Seed(1)
func createdTokenSecret(overrideName ...string) *v1.Secret {
return namedCreatedTokenSecret("default-token-stdpg")
return namedCreatedTokenSecret("default-token-xn8fg")
}
// namedTokenSecret returns the ServiceAccountToken secret posted when creating a new token secret with the given name.
@@ -264,12 +264,12 @@ func TestTokenCreation(t *testing.T) {
// Attempt 2
core.NewGetAction(schema.GroupVersionResource{Version: "v1", Resource: "serviceaccounts"}, metav1.NamespaceDefault, "default"),
core.NewCreateAction(schema.GroupVersionResource{Version: "v1", Resource: "secrets"}, metav1.NamespaceDefault, namedCreatedTokenSecret("default-token-jk9rt")),
core.NewCreateAction(schema.GroupVersionResource{Version: "v1", Resource: "secrets"}, metav1.NamespaceDefault, namedCreatedTokenSecret("default-token-txhzt")),
// Attempt 3
core.NewGetAction(schema.GroupVersionResource{Version: "v1", Resource: "serviceaccounts"}, metav1.NamespaceDefault, "default"),
core.NewCreateAction(schema.GroupVersionResource{Version: "v1", Resource: "secrets"}, metav1.NamespaceDefault, namedCreatedTokenSecret("default-token-684pg")),
core.NewUpdateAction(schema.GroupVersionResource{Version: "v1", Resource: "serviceaccounts"}, metav1.NamespaceDefault, serviceAccount(addNamedTokenSecretReference(emptySecretReferences(), "default-token-684pg"))),
core.NewCreateAction(schema.GroupVersionResource{Version: "v1", Resource: "secrets"}, metav1.NamespaceDefault, namedCreatedTokenSecret("default-token-vnmz7")),
core.NewUpdateAction(schema.GroupVersionResource{Version: "v1", Resource: "serviceaccounts"}, metav1.NamespaceDefault, serviceAccount(addNamedTokenSecretReference(emptySecretReferences(), "default-token-vnmz7"))),
},
},
"new serviceaccount with no secrets encountering unending create error": {
@@ -293,10 +293,10 @@ func TestTokenCreation(t *testing.T) {
core.NewCreateAction(schema.GroupVersionResource{Version: "v1", Resource: "secrets"}, metav1.NamespaceDefault, createdTokenSecret()),
// Retry 1
core.NewGetAction(schema.GroupVersionResource{Version: "v1", Resource: "serviceaccounts"}, metav1.NamespaceDefault, "default"),
core.NewCreateAction(schema.GroupVersionResource{Version: "v1", Resource: "secrets"}, metav1.NamespaceDefault, namedCreatedTokenSecret("default-token-jk9rt")),
core.NewCreateAction(schema.GroupVersionResource{Version: "v1", Resource: "secrets"}, metav1.NamespaceDefault, namedCreatedTokenSecret("default-token-txhzt")),
// Retry 2
core.NewGetAction(schema.GroupVersionResource{Version: "v1", Resource: "serviceaccounts"}, metav1.NamespaceDefault, "default"),
core.NewCreateAction(schema.GroupVersionResource{Version: "v1", Resource: "secrets"}, metav1.NamespaceDefault, namedCreatedTokenSecret("default-token-684pg")),
core.NewCreateAction(schema.GroupVersionResource{Version: "v1", Resource: "secrets"}, metav1.NamespaceDefault, namedCreatedTokenSecret("default-token-vnmz7")),
},
},
"new serviceaccount with missing secrets": {