[Docs] Document that sparse histograms may have labels specified in enums.xml.
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Bug: none
Change-Id: Iab575b2a8802f99161265adbf41c5ceaa2b180fb
Reviewed-on: https://chromium-review.googlesource.com/815543
Reviewed-by: Mark Pearson <[email protected]>
Commit-Queue: Ilya Sherman <[email protected]>
Cr-Commit-Position: refs/heads/master@{#522667}diff --git a/tools/metrics/histograms/README.md b/tools/metrics/histograms/README.md
index a48e281..065c291d 100644
--- a/tools/metrics/histograms/README.md
+++ b/tools/metrics/histograms/README.md
@@ -240,11 +240,18 @@
tools not to treat the partial base name as a distinct histogram. Note that
suffixes can be applied recursively.
+### Enum labels
+
+_All_ histograms, including boolean and sparse histograms, may have enum labels
+provided via [enums.xml](./enums.xml). Using labels is encouraged whenever
+labels would be clearer than raw numeric values.
+
## When To Use Sparse Histograms
Sparse histograms are well suited for recording counts of exact sample values
that are sparsely distributed over a large range. They can be used with enums
-as well as regular integer values.
+as well as regular integer values. It is often valuable to provide labels in
+[enums.xml](./enums.xml).
The implementation uses a lock and a map, whereas other histogram types use a
vector and no lock. It is thus more costly to add values to, and each value
