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Content-class: urn:content-classes:message
Subject: [RFC] Define well known packet burst sizes
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Date: Sat, 12 Oct 2024 14:35:46 +0200
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Thread-Topic: [RFC] Define well known packet burst sizes
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From: =?iso-8859-1?Q?Morten_Br=F8rup?= <mb@smartsharesystems.com>
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We should define some "well known" packet burst sizes in rte_config.h.

Especially the default packet burst size is interesting;
if known at compile time, various drivers and libraries can optimize for =
it (i.e. special handling for nb_pkts =3D=3D RTE_PKT_BURST_DEFAULT).

It should also be used in DPDK examples and apps, instead of defining =
MAX_PKT_BURST in each and everyone.


Specifically:

/**
 * Default packet burst size.
 *
 * Also intended for optimizing packet processing (e.g. by loop =
unrolling).
 */
#define RTE_PKT_BURST_DEFAULT 32

/**
 * Largest packet burst size guaranteed to be supported throughout DPDK.
 *
 * Also intended for sizing large temporary arrays of mbufs, e.g. in =
rte_pktmbuf_free_bulk().
 */
#define RTE_PKT_BURST_MAX 512
#define RTE_MEMPOOL_CACHE_MAX_SIZE RTE_PKT_BURST_MAX

/**
 * Smallest packet burst size recommended for latency sensitive =
applications, when throughput still matters.
 *
 * Also intended for sizing small staging arrays of mbufs, e.g. in =
drivers.
 *
 * Note: Corresponds to one CPU cache line of object pointers.
 *  - 8 on most 64 bit architectures, 16 on POWER architecture (ppc_64).
 *  - 16 on all 32 bit architectures.
 */
#define RTE_PKT_BURST_SMALL (RTE_CACHE_LINE_SIZE / sizeof(void *))