Re: [dpdk-dev] [PATCH 0/4] eal/common: introduce rte_memset and related test

[Maxime Coquelin <maxime.coquelin@redhat.com>]

Hi Zhiyong,

On 12/05/2016 09:26 AM, Zhiyong Yang wrote:
> DPDK code has met performance drop badly in some case when calling glibc
> function memset. Reference to discussions about memset in
> http://dpdk.org/ml/archives/dev/2016-October/048628.html
> It is necessary to introduce more high efficient function to fix it.
> One important thing about rte_memset is that we can get clear control
> on what instruction flow is used.
>
> This patchset introduces rte_memset to bring more high efficient
> implementation, and will bring obvious perf improvement, especially
> for small N bytes in the most application scenarios.
>
> Patch 1 implements rte_memset in the file rte_memset.h on IA platform
> The file supports three types of instruction sets including sse & avx
> (128bits), avx2(256bits) and avx512(512bits). rte_memset makes use of
> vectorization and inline function to improve the perf on IA. In addition,
> cache line and memory alignment are fully taken into consideration.
>
> Patch 2 implements functional autotest to validates the function whether
> to work in a right way.
>
> Patch 3 implements performance autotest separately in cache and memory.
>
> Patch 4 Using rte_memset instead of copy_virtio_net_hdr can bring 3%~4%
> performance improvements on IA platform from virtio/vhost non-mergeable
> loopback testing.
>
> Zhiyong Yang (4):
>   eal/common: introduce rte_memset on IA platform
>   app/test: add functional autotest for rte_memset
>   app/test: add performance autotest for rte_memset
>   lib/librte_vhost: improve vhost perf using rte_memset
>
>  app/test/Makefile                                  |   3 +
>  app/test/test_memset.c                             | 158 +++++++++
>  app/test/test_memset_perf.c                        | 348 +++++++++++++++++++
>  doc/guides/rel_notes/release_17_02.rst             |  11 +
>  .../common/include/arch/x86/rte_memset.h           | 376 +++++++++++++++++++++
>  lib/librte_eal/common/include/generic/rte_memset.h |  51 +++
>  lib/librte_vhost/virtio_net.c                      |  18 +-
>  7 files changed, 958 insertions(+), 7 deletions(-)
>  create mode 100644 app/test/test_memset.c
>  create mode 100644 app/test/test_memset_perf.c
>  create mode 100644 lib/librte_eal/common/include/arch/x86/rte_memset.h
>  create mode 100644 lib/librte_eal/common/include/generic/rte_memset.h
>

Thanks for the series, idea looks good to me.

Wouldn't be worth to also use rte_memset in Virtio PMD (not
compiled/tested)? :

diff --git a/drivers/net/virtio/virtio_rxtx.c 
b/drivers/net/virtio/virtio_rxtx.c
index 22d97a4..a5f70c4 100644
--- a/drivers/net/virtio/virtio_rxtx.c
+++ b/drivers/net/virtio/virtio_rxtx.c
@@ -287,7 +287,7 @@ virtqueue_enqueue_xmit(struct virtnet_tx *txvq, 
struct rte_mbuf *cookie,
                         rte_pktmbuf_prepend(cookie, head_size);
                 /* if offload disabled, it is not zeroed below, do it 
now */
                 if (offload == 0)
-                       memset(hdr, 0, head_size);
+                       rte_memset(hdr, 0, head_size);
         } else if (use_indirect) {
                 /* setup tx ring slot to point to indirect
                  * descriptor list stored in reserved region.

Cheers,
Maxime