On Fri, Jul 10, 2020 at 10:21:40AM +0200, Morten Brørup wrote: > 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 >
AFAIK: the NICs supported by the ixgbe driver only allow the size to be specified in KB granularity. However, it may be safe to have a driver modification whereby anything over 1600 bytes is considered as 2KB if jumbo frame support is disabled. I don't think anyone has actually looked into doing so though, or if there are other hidden gotchas about attempting to do so. /Bruce
