Sep 12 – 14, 2022
Europe/Dublin timezone

Percpu hashtab traversal measurement study

Sep 13, 2022, 6:00 PM
"Pembroke" (Clayton Hotel on Burlington Road)


Clayton Hotel on Burlington Road

eBPF & Networking Track eBPF & Networking


Brian Vazquez (Google)


As platforms grow in cpu count (200+ cpu), using per cpu data structures is becoming more and more expensive. Copying the percpu data from the bpf hashtab map to userspace buffers can take up to 22 us per entry on a platform with 256 cores.

This talk presents a detailed measurement study of the cost of percpu hashtab traversal, covering various methods and systems with core counts.
We will discuss how the current implementation of this data structure makes it hard to amortize cache misses, and solicit proposal for possible enhancements.

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Primary author

Brian Vazquez (Google)


Luigi Rizzo (Google) Stanislav Fomichev (Google) Sagarika Sharma (Columbia University)

Presentation materials

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