From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maxime Coquelin Subject: Re: [PATCH 05/10] net/virtio: refactor virtqueue structure Date: Tue, 19 Mar 2019 14:28:30 +0100 Message-ID: References: <20190319064312.13743-1-tiwei.bie@intel.com> <20190319064312.13743-6-tiwei.bie@intel.com> <20190319094432.iap4i7ffs6soukr7@jenstp.localdomain> <20190319100939.GA3839@dpdk-tbie.sh.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: zhihong.wang@intel.com, dev@dpdk.org To: Tiwei Bie , Jens Freimann Return-path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by dpdk.org (Postfix) with ESMTP id 74BEBA3 for ; Tue, 19 Mar 2019 14:28:34 +0100 (CET) In-Reply-To: <20190319100939.GA3839@dpdk-tbie.sh.intel.com> Content-Language: en-US List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On 3/19/19 11:09 AM, Tiwei Bie wrote: > On Tue, Mar 19, 2019 at 10:44:32AM +0100, Jens Freimann wrote: >> On Tue, Mar 19, 2019 at 02:43:07PM +0800, Tiwei Bie wrote: >>> Put split ring and packed ring specific fields into separate >>> sub-structures, and also union them as they won't be available >>> at the same time. >>> >>> Signed-off-by: Tiwei Bie >>> --- >>> drivers/net/virtio/virtio_ethdev.c | 71 +++++++++--------- >>> drivers/net/virtio/virtio_rxtx.c | 66 ++++++++--------- >>> drivers/net/virtio/virtio_rxtx_simple.h | 2 +- >>> drivers/net/virtio/virtio_rxtx_simple_neon.c | 2 +- >>> drivers/net/virtio/virtio_rxtx_simple_sse.c | 2 +- >>> drivers/net/virtio/virtqueue.c | 6 +- >>> drivers/net/virtio/virtqueue.h | 77 +++++++++++--------- >>> 7 files changed, 117 insertions(+), 109 deletions(-) >>> >> [snip] >> ... >>> diff --git a/drivers/net/virtio/virtqueue.h b/drivers/net/virtio/virtqueue.h >>> index 80c0c43c3..48b3912e6 100644 >>> --- a/drivers/net/virtio/virtqueue.h >>> +++ b/drivers/net/virtio/virtqueue.h >>> @@ -191,17 +191,22 @@ struct vq_desc_extra { >>> >>> struct virtqueue { >>> struct virtio_hw *hw; /**< virtio_hw structure pointer. */ >>> - struct vring vq_ring; /**< vring keeping desc, used and avail */ >>> - struct vring_packed ring_packed; /**< vring keeping descs */ >>> - bool used_wrap_counter; >>> - uint16_t cached_flags; /**< cached flags for descs */ >>> - uint16_t event_flags_shadow; >>> + union { >>> + struct { >>> + /**< vring keeping desc, used and avail */ >>> + struct vring ring; >>> + } vq_split; >>> >>> - /** >>> - * Last consumed descriptor in the used table, >>> - * trails vq_ring.used->idx. >>> - */ >>> - uint16_t vq_used_cons_idx; >>> + struct { >>> + /**< vring keeping descs and events */ >>> + struct vring_packed ring; >>> + bool used_wrap_counter; >>> + uint16_t cached_flags; /**< cached flags for descs */ >>> + uint16_t event_flags_shadow; >>> + } vq_packed; >>> + }; >>> + >>> + uint16_t vq_used_cons_idx; /**< last consumed descriptor */ >>> uint16_t vq_nentries; /**< vring desc numbers */ >>> uint16_t vq_free_cnt; /**< num of desc available */ >>> uint16_t vq_avail_idx; /**< sync until needed */ >> >> Honest question: What do we really gain by putting it in a union? We >> save a little memory. But we also make code less readable IMHO. > > I think it will make it clear that fields like used_wrap_counter > are only available in packed ring which will make the code more > readable. > >> >> If we do this, can we at least shorten some variable names, like drop >> the vq_ prefix? (It's used everywhere like vq->vq_packed*, so with >> vq->packed* we don't loose any context). > > I prefer to have consistent prefix like most fields in this > structure (although some fields don't really follow this). As Jens, I tend to agree that the vq_ prefix is quite redundant. However, I think it is better to keep it in this patch for consistency. Maybe it can be remove in a separate patch later? > Thanks, > Tiwei > >> >> I'm not strictly against this change but I'm wondering if it's worth >> it. >> >> regards, >> Jens >>