[dpdk-dev] [PATCH v2 00/16] vhost packed ring performance optimization
Gavin Hu (Arm Technology China)
Gavin.Hu at arm.com
Mon Sep 23 11:05:12 CEST 2019
A general comment for the series, could you mark V1 Superseded?
> -----Original Message-----
> From: dev <dev-bounces at dpdk.org> On Behalf Of Marvin Liu
> Sent: Friday, September 20, 2019 12:36 AM
> To: maxime.coquelin at redhat.com; tiwei.bie at intel.com;
> zhihong.wang at intel.com
> Cc: dev at dpdk.org; Marvin Liu <yong.liu at intel.com>
> Subject: [dpdk-dev] [PATCH v2 00/16] vhost packed ring performance
> Packed ring has more compact ring format and thus can significantly
> reduce the number of cache miss. It can lead to better performance.
> This has been approved in virtio user driver, on normal E5 Xeon cpu
> single core performance can raise 12%.
> However vhost performance with packed ring performance was decreased.
> Through analysis, mostly extra cost was from the calculating of each
> descriptor flag which depended on ring wrap counter. Moreover, both
> frontend and backend need to write same descriptors which will cause
> cache contention. Especially when doing vhost enqueue function, virtio
> refill packed ring function may write same cache line when vhost doing
> enqueue function. This kind of extra cache cost will reduce the benefit
> of reducing cache misses.
> For optimizing vhost packed ring performance, vhost enqueue and dequeue
> function will be splitted into fast and normal path.
> Several methods will be taken in fast path:
> Uroll burst loop function into more pieces.
> Handle descriptors in one cache line simultaneously.
> Prerequisite check that whether I/O space can copy directly into mbuf
> space and vice versa.
> Prerequisite check that whether descriptor mapping is successful.
> Distinguish vhost used ring update function by enqueue and dequeue
> Buffer dequeue used descriptors as many as possible.
> Update enqueue used descriptors by cache line.
> Cache memory region structure for fast conversion.
> Disable sofware prefetch is hardware can do better.
> After all these methods done, single core vhost PvP performance with 64B
> packet on Xeon 8180 can boost 40%.
> - Utilize compiler's pragma to unroll loop, distinguish clang/icc/gcc
> - Buffered dequeue used desc number changed to (RING_SZ - PKT_BURST)
> - Optimize dequeue used ring update when in_order negotiated
> Marvin Liu (16):
> vhost: add single packet enqueue function
> vhost: unify unroll pragma parameter
> vhost: add burst enqueue function for packed ring
> vhost: add single packet dequeue function
> vhost: add burst dequeue function
> vhost: rename flush shadow used ring functions
> vhost: flush vhost enqueue shadow ring by burst
> vhost: add flush function for burst enqueue
> vhost: buffer vhost dequeue shadow ring
> vhost: split enqueue and dequeue flush functions
> vhost: optimize enqueue function of packed ring
> vhost: add burst and single zero dequeue functions
> vhost: optimize dequeue function of packed ring
> vhost: cache address translation result
> vhost: check whether disable software pre-fetch
> vhost: optimize packed ring dequeue when in-order
> lib/librte_vhost/Makefile | 24 +
> lib/librte_vhost/rte_vhost.h | 27 +
> lib/librte_vhost/vhost.h | 33 +
> lib/librte_vhost/virtio_net.c | 1071 +++++++++++++++++++++++++++------
> 4 files changed, 960 insertions(+), 195 deletions(-)
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