[dpdk-dev] [PATCH v2 02/24] virtio: Use weaker barriers

2015-01-28 Thread Ouyang, Changchun
> -Original Message- > From: Xie, Huawei > Sent: Wednesday, January 28, 2015 12:16 AM > To: Stephen Hemminger > Cc: Ouyang, Changchun; dev at dpdk.org > Subject: RE: [dpdk-dev] [PATCH v2 02/24] virtio: Use weaker barriers > > > > > -Original Message

[dpdk-dev] [PATCH v2 02/24] virtio: Use weaker barriers

2015-01-27 Thread Xie, Huawei
> -Original Message- > From: Stephen Hemminger [mailto:stephen at networkplumber.org] > Sent: Tuesday, January 27, 2015 5:59 PM > To: Xie, Huawei > Cc: Ouyang, Changchun; dev at dpdk.org > Subject: Re: [dpdk-dev] [PATCH v2 02/24] virtio: Use weaker barriers >

[dpdk-dev] [PATCH v2 02/24] virtio: Use weaker barriers

2015-01-27 Thread Stephen Hemminger
> I recall our original code is virtio_wmb(). > Use store fence to ensure all updates to entries before updating the index. > Why do we need virtio_rmb() here and add virtio_wmb after > vq_update_avail_idx()? Store fence is unnecessary, Intel CPU's are cache coherent, please read the virtio

[dpdk-dev] [PATCH v2 02/24] virtio: Use weaker barriers

2015-01-27 Thread Ouyang, Changchun
: Stephen Hemminger (stephen at networkplumber.org) Subject: RE: [dpdk-dev] [PATCH v2 02/24] virtio: Use weaker barriers >---if (likely(nb_enqueued)) { >--->---virtio_wmb(); >--->---if (unlikely(virtqueue_kick_prepare(rxvq))) { >--->--->

[dpdk-dev] [PATCH v2 02/24] virtio: Use weaker barriers

2015-01-27 Thread Xie, Huawei
> -Original Message- > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Ouyang Changchun > Sent: Tuesday, January 27, 2015 10:36 AM > To: dev at dpdk.org > Subject: [dpdk-dev] [PATCH v2 02/24] virtio: Use weaker barriers > > The DPDK driver only has