[dpdk-dev] [PATCH v2 3/3] vhost: optimize vhost virtqueue struct
Maxime Coquelin
maxime.coquelin at redhat.com
Wed Mar 17 11:26:49 CET 2021
On 3/16/21 2:38 PM, David Marchand wrote:
> On Tue, Mar 16, 2021 at 1:42 PM Maxime Coquelin
> <maxime.coquelin at redhat.com> wrote:
>>
>> This patch moves vhost_virtuqueue struct fields in order
>
> virtqueue
> You might want to add something in your local dictionary :-p.
>
>
>> to both optimize packing and move hot fields on the first
>> cachelines.
>>
>> Signed-off-by: Maxime Coquelin <maxime.coquelin at redhat.com>
>> ---
>> lib/librte_vhost/vhost.h | 52 +++++++++++++++++++++-------------------
>> 1 file changed, 27 insertions(+), 25 deletions(-)
>>
>> diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
>> index 3a71dfeed9..ae45b05dd1 100644
>> --- a/lib/librte_vhost/vhost.h
>> +++ b/lib/librte_vhost/vhost.h
>> @@ -133,7 +133,7 @@ struct vhost_virtqueue {
>> struct vring_used *used;
>> struct vring_packed_desc_event *device_event;
>> };
>> - uint32_t size;
>> + uint16_t size;
>
> There is one site in the code that could be problematic:
>
> vhost_user_set_vring_num()
> ...
> vq->size = msg->payload.state.num;
> ...
> if (vq->size > 32768) {
>
> payload.state.num is an unsigned int, so we'd better check its value
> as an unsigned int, before storing to vq->size.
Indeed, I will rework the function, so that it checks that
msg->payload.state.num is smaller than 32K to comply with the spec,
and so remove the later check on vq->size.
>
>>
>> uint16_t last_avail_idx;
>> uint16_t last_used_idx;
>> @@ -143,29 +143,12 @@ struct vhost_virtqueue {
>> #define VIRTIO_INVALID_EVENTFD (-1)
>> #define VIRTIO_UNINITIALIZED_EVENTFD (-2)
>>
>> - int enabled;
>> - int access_ok;
>> - int ready;
>> - int notif_enable;
>> -#define VIRTIO_UNINITIALIZED_NOTIF (-1)
>> + bool enabled;
>> + bool access_ok;
>> + bool ready;
>
> Changing those types is fine, but it is a bit odd to still see
> boolean_var = 0 or boolean_var = 1 in the rest of the code.
Yes, I fix all the places with assigning boolean values.
>
>>
>> rte_spinlock_t access_lock;
>>
>> - /* Used to notify the guest (trigger interrupt) */
>> - int callfd;
>> - /* Currently unused as polling mode is enabled */
>> - int kickfd;
>> -
>> - /* Physical address of used ring, for logging */
>> - uint64_t log_guest_addr;
>> -
>> - /* inflight share memory info */
>> - union {
>> - struct rte_vhost_inflight_info_split *inflight_split;
>> - struct rte_vhost_inflight_info_packed *inflight_packed;
>> - };
>> - struct rte_vhost_resubmit_info *resubmit_inflight;
>> - uint64_t global_counter;
>>
>> union {
>> struct vring_used_elem *shadow_used_split;
>> @@ -176,22 +159,36 @@ struct vhost_virtqueue {
>> uint16_t shadow_aligned_idx;
>> /* Record packed ring first dequeue desc index */
>> uint16_t shadow_last_used_idx;
>> - struct vhost_vring_addr ring_addrs;
>>
>> - struct batch_copy_elem *batch_copy_elems;
>> uint16_t batch_copy_nb_elems;
>> + struct batch_copy_elem *batch_copy_elems;
>> bool used_wrap_counter;
>> bool avail_wrap_counter;
>>
>> - struct log_cache_entry *log_cache;
>> + /* Physical address of used ring, for logging */
>> uint16_t log_cache_nb_elem;
>
> Indent is broken / not consistent, probably because you cut/pasted lines.
Will fix it.
Thanks,
Maxime
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