> -----Original Message----- > From: Morten Brørup <m...@smartsharesystems.com> > Sent: 2022年9月7日 22:47 > To: Ma, WenwuX <wenwux...@intel.com>; maxime.coque...@redhat.com; > Xia, Chenbo <chenbo....@intel.com>; dev@dpdk.org; Richardson, Bruce > <bruce.richard...@intel.com> > Cc: Pai G, Sunil <sunil.pa...@intel.com>; Hu, Jiayu <jiayu...@intel.com>; > Wang, Yinan <yinan.w...@intel.com>; He, Xingguang > <xingguang...@intel.com>; Ding, Xuan <xuan.d...@intel.com>; Jiang, > Cheng1 <cheng1.ji...@intel.com>; Wang, YuanX <yuanx.w...@intel.com> > Subject: RE: [PATCH v4] vhost: support CPU copy for small packets > > > From: Wenwu Ma [mailto:wenwux...@intel.com] > > Sent: Monday, 29 August 2022 02.57 > > > > Offloading small packets to DMA degrades throughput 10%~20%, and this > > is because DMA offloading is not free and DMA is not good at > > processing small packets. In addition, control plane packets are > > usually small, and assign those packets to DMA will significantly > > increase latency, which may cause timeout like TCP handshake packets. > > Therefore, this patch use CPU to perform small copies in vhost. > > > > Signed-off-by: Wenwu Ma <wenwux...@intel.com> > > --- > > [...] > > > diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c index > > 35fa4670fd..cf796183a0 100644 > > --- a/lib/vhost/virtio_net.c > > +++ b/lib/vhost/virtio_net.c > > @@ -26,6 +26,8 @@ > > > > #define MAX_BATCH_LEN 256 > > > > +#define CPU_COPY_THRESHOLD_LEN 256 > > This threshold may not be optimal for all CPU architectures and/or DMA > engines. > > Could you please provide a test application to compare the performance of > DMA copy with CPU rte_memcpy? > > The performance metric should be simple: How many cycles does the CPU > spend copying various packet sizes using each the two methods. > > You could provide test_dmadev_perf.c in addition to the existing > test_dmadev.c. > You can probably copy a some of the concepts and code from > test_memcpy_perf.c. > Alternatively, you might be able to add DMA copy to test_memcpy_perf.c. > > I'm sorry to push this on you - it should have been done as part of DMAdev > development already. > > -Morten
The test application has been supported by the following patch. http://patchwork.dpdk.org/project/dpdk/patch/20220919113957.52127-1-cheng1.ji...@intel.com/
