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To: Jens Freimann <jfreimann@redhat.com>
Cc: Tiwei Bie <tiwei.bie@intel.com>, zhihong.wang@intel.com, dev@dpdk.org
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From: Maxime Coquelin <maxime.coquelin@redhat.com>
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Subject: Re: [dpdk-dev] [PATCH 05/10] net/virtio: refactor virtqueue
structure
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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 <tiwei.bie@intel.com>
>>>>> ---
>>>>> 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
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To: Jens Freimann <jfreimann@redhat.com>
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References: <20190319064312.13743-1-tiwei.bie@intel.com>
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<20190319134751.ibgaalfravjm77lh@jenstp.localdomain>
From: Maxime Coquelin <maxime.coquelin@redhat.com>
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Subject: Re: [dpdk-dev] [PATCH 05/10] net/virtio: refactor virtqueue
structure
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Message-ID: <20190319135050.xliWcsaNyV8Fd0NZUE5HvzbthdaYRJ0jfH8MHSpHSys@z>
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 <tiwei.bie@intel.com>
>>>>> ---
>>>>> 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