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Date: Sat, 2 Mar 2024 08:37:34 -0800
From: Stephen Hemminger <stephen@networkplumber.org>
To: Morten =?UTF-8?B?QnLDuHJ1cA==?= <mb@smartsharesystems.com>
Cc: Mattias =?UTF-8?B?UsO2bm5ibG9t?= <hofors@lysator.liu.se>, <dev@dpdk.org>
Subject: Re: [PATCH v2 00/71] replace use of fixed size rte_mempcy
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On Sat, 2 Mar 2024 14:05:45 +0100
Morten Br=C3=B8rup <mb@smartsharesystems.com> wrote:
> > =20
> > > My experience with replacing rte_memcpy() with memcpy() (or vice =20
> > versa) =20
> > > is mixed.
> > >
> > > I've also tried just dropping the DPDK-custom memcpy() implementation
> > > altogether, and that caused a performance drop (in a particular app, =
=20
> > on =20
> > > a particular compiler and CPU). =20
>=20
> I guess the compilers are just not where we want them to be yet.
>=20
> I don't mind generally replacing rte_memcpy() with memcpy() in the contro=
l plane.
> But we should use whatever is more efficient in the data plane.
>=20
> We must also keep in mind that DPDK supports old distros with old compile=
rs. We should not remove a superfluous hand crafted optimization if a suppo=
rted old compiler hasn't caught up with it yet, i.e. if it isn't superfluou=
s on some of the old compilers supported by DPDK.
When I scanned the result.
1. Most copies were small (like Ether address or IPv6 address) and compiler
inlining should beat a function call every time.
2. Larger structure copies were in control path.