Re: [PATCH v4 00/13] Optionally have rte_memcpy delegate to compiler memcpy

["Mattias Rönnblom" <hofors@lysator.liu.se>]

On Tue, Jun 25, 2024 at 05:29:35PM +0200, Maxime Coquelin wrote:
> Hi Mattias,
> 
> On 6/20/24 19:57, Mattias Rönnblom wrote:
> > This patch set make DPDK library, driver, and application code use the
> > compiler/libc memcpy() by default when functions in <rte_memcpy.h> are
> > invoked.
> > 
> > The various custom DPDK rte_memcpy() implementations may be retained
> > by means of a build-time option.
> > 
> > This patch set only make a difference on x86, PPC and ARM. Loongarch
> > and RISCV already used compiler/libc memcpy().
> 
> It indeed makes a difference on x86!
>
> Just tested latest main with and without your series on
> Intel(R) Xeon(R) Gold 6438N.
> 
> The test is a simple IO loop between a Vhost PMD and a Virtio-user PMD:
> # dpdk-testpmd -l 4-6   --file-prefix=virtio1 --no-pci --vdev 'net_virtio_user0,mac=00:01:02:03:04:05,path=./vhost-net,server=1,mrg_rxbuf=1,in_order=1'
> --single-file-segments -- -i
> testpmd> start
> 
> # dpdk-testpmd -l 8-10   --file-prefix=vhost1 --no-pci --vdev
> 'net_vhost0,iface=vhost-net,client=1'   --single-file-segments -- -i
> testpmd> start tx_first 32
> 
> Latest main: 14.5Mpps
> Latest main + this series: 10Mpps
>

I ran the above benchmark on my Raptor Lake desktop (locked to 3,2
GHz). GCC 12.3.0.

Core use_cc_memcpy Mpps
E    false         9.5
E    true          9.7
P    false         16.4
P    true          13.5

On the P-cores, there's a significant performance regression, although
not as bad as the one you see on your Sapphire Rapids Xeon. On the
E-cores, there's actually a slight performance gain.

The virtio PMD does not directly invoke rte_memcpy() or anything else
from <rte_memcpy.h>, but rather use memcpy(), so I'm not sure I
understand what's going on here. Does the virtio driver delegate some
performance-critical task to some module that in turns uses
rte_memcpy()?

> So for me, it should be disabled by default.
> 
> Regards,
> Maxime
> 
> > This patch set includes a number of fixes in drivers and libraries
> > which errornously relied on <rte_memcpy.h> including header files
> > (i.e., <rte_vect.h>) required by its implementation.
> > 
> > Mattias Rönnblom (13):
> >    net/i40e: add missing vector API header include
> >    net/iavf: add missing vector API header include
> >    net/ice: add missing vector API header include
> >    net/ixgbe: add missing vector API header include
> >    net/ngbe: add missing vector API header include
> >    net/txgbe: add missing vector API header include
> >    net/virtio: add missing vector API header include
> >    net/fm10k: add missing vector API header include
> >    event/dlb2: include headers for vector and memory copy APIs
> >    net/octeon_ep: add missing vector API header include
> >    distributor: add missing vector API header include
> >    fib: add missing vector API header include
> >    eal: provide option to use compiler memcpy instead of RTE
> > 
> >   config/meson.build                          |  1 +
> >   doc/guides/rel_notes/release_24_07.rst      | 21 +++++++
> >   drivers/event/dlb2/dlb2.c                   |  2 +
> >   drivers/net/fm10k/fm10k_rxtx_vec.c          |  3 +-
> >   drivers/net/i40e/i40e_rxtx_vec_sse.c        |  3 +-
> >   drivers/net/iavf/iavf_rxtx_vec_sse.c        |  3 +-
> >   drivers/net/ice/ice_rxtx_vec_sse.c          |  2 +-
> >   drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c      |  3 +-
> >   drivers/net/ngbe/ngbe_rxtx_vec_sse.c        |  3 +-
> >   drivers/net/octeon_ep/otx_ep_ethdev.c       |  2 +
> >   drivers/net/txgbe/txgbe_rxtx_vec_sse.c      |  3 +-
> >   drivers/net/virtio/virtio_rxtx_simple_sse.c |  3 +-
> >   lib/distributor/rte_distributor.c           |  1 +
> >   lib/eal/arm/include/rte_memcpy.h            | 10 ++++
> >   lib/eal/include/generic/rte_memcpy.h        | 61 ++++++++++++++++++---
> >   lib/eal/loongarch/include/rte_memcpy.h      | 53 ++----------------
> >   lib/eal/ppc/include/rte_memcpy.h            | 10 ++++
> >   lib/eal/riscv/include/rte_memcpy.h          | 53 ++----------------
> >   lib/eal/x86/include/meson.build             |  1 +
> >   lib/eal/x86/include/rte_memcpy.h            | 11 +++-
> >   lib/fib/trie.c                              |  1 +
> >   meson_options.txt                           |  2 +
> >   22 files changed, 131 insertions(+), 121 deletions(-)
> > 
>