> -----Original Message----- > From: Morten Brørup <[email protected]> > Sent: 2022年9月7日 22:47 > To: Ma, WenwuX <[email protected]>; [email protected]; > Xia, Chenbo <[email protected]>; [email protected]; Richardson, Bruce > <[email protected]> > Cc: Pai G, Sunil <[email protected]>; Hu, Jiayu <[email protected]>; > Wang, Yinan <[email protected]>; He, Xingguang > <[email protected]>; Ding, Xuan <[email protected]>; Jiang, > Cheng1 <[email protected]>; Wang, YuanX <[email protected]> > Subject: RE: [PATCH v4] vhost: support CPU copy for small packets > > > From: Wenwu Ma [mailto:[email protected]] > > 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 <[email protected]> > > --- > > [...] > > > 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/[email protected]/
