> -----Original Message----- > From: Jason Wang [mailto:jasow...@redhat.com] > Sent: Wednesday, July 10, 2019 12:28 PM > To: Liu, Yong <yong....@intel.com>; Bie, Tiwei <tiwei....@intel.com>; > maxime.coque...@redhat.com; dev@dpdk.org > Subject: Re: [dpdk-dev] [RFC PATCH 02/13] add vhost packed ring fast enqueue > function > > > On 2019/7/9 上午1:13, Marvin Liu wrote: > > In fast enqueue function, will first check whether descriptors are > > cache aligned. Fast enqueue function will check prerequisites in the > > beginning. Fast enqueue function do not support chained mbufs, normal > > function will handle that. > > > > Signed-off-by: Marvin Liu <yong....@intel.com> > > Any reason for not letting compiler to unroll the loops? >
Hi Jason, I'm not sure about how much compiler can help on unrolling loops as it can't know how much loops will create in one call. After force not using unroll-loop optimization by "-fno-unroll-loops", virtio_dev_rx_packed function size remained the same. So look like gcc unroll-loop optimization do not help here. And fast enqueue function not only did unroll loop, it also checked cache alignment which can help performance in another side. Regards, Marvin > Thanks >
