api: Reduce allocations of Attributes.Builder #12276
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Modifying existing Attributes was virtually guaranteed to allocate within build(), just because `base` was not considered for the new map size. Discard was also allocation-heavy because it often created a new map. Using a regular copy-on-write approach is enough to avoid the unnecessary allocations in both cases. This was noticed in a profile that included xds's AddressFilter.setPathFilter(), where Attributes.Builder.build() allocated 6x the memory of Attributes.Builder.data(). b/435208946#comment41
kannanjgithub
approved these changes
Aug 26, 2025
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Modifying existing Attributes was virtually guaranteed to allocate within build(), just because
basewas not considered for the new map size. Discard was also allocation-heavy because it often created a new map. Using a regular copy-on-write approach is enough to avoid the unnecessary allocations in both cases.This was noticed in a profile that included xds's
AddressFilter.setPathFilter(), where Attributes.Builder.build() allocated 6x the memory of Attributes.Builder.data().
b/435208946#comment41