[dpdk-dev] Weird 2 KB MBUF data room requirement

Morten Brørup mb at smartsharesystems.com
Fri Jul 10 10:21:40 CEST 2020


Dear Ethernet PMD developers,

According to rte_mbuf_core.h, RTE_MBUF_DEFAULT_DATAROOM is 2048 bytes because some NICs need at least 2 KB buffer to receive standard Ethernet frames without splitting them into multiple segments.

This is a serious waste of memory, considering that standard Ethernet frames are max 1518 bytes.

How wide spread is this limitation... is it common or a rare exception?

Where is it documented which NICs suffer from this limitation?

Do any Intel NICs suffer from this limitation?


NB: We are targeting an MBUF total size (incl. memzone element overhead) of 2^N, and this limitation would increase our MBUF total size to 4 KB.


Med venlig hilsen / kind regards
- Morten Brørup



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