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 14:50:50 +0100 Message-ID: <1d05e311-c60b-cb1d-ff2b-974e01a0451b@redhat.com> 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> <20190319134751.ibgaalfravjm77lh@jenstp.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Cc: Tiwei Bie , zhihong.wang@intel.com, dev@dpdk.org To: Jens Freimann Return-path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by dpdk.org (Postfix) with ESMTP id 0823F2C60 for ; Tue, 19 Mar 2019 14:50:58 +0100 (CET) In-Reply-To: <20190319134751.ibgaalfravjm77lh@jenstp.localdomain> 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 2:47 PM, Jens Freimann wrote: > On Tue, Mar 19, 2019 at 02:28:30PM +0100, Maxime Coquelin wrote: >> >> >> 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? > > I thought it might be convenient to change it now as we are touching > all related code anyway. But I also don't want to block the patch > because of > this cosmetic thing. So let's defer it to a later patch set. OK, when I meant later, I meant to remove vq_ prefix for all fields, not only vq_split & vq_packed. But yes, that's just cosmetic so let's keep it as is for now. > > regards, > Jens