On 6/13/2024 11:32 AM, Konstantin Ananyev wrote:
>
>
>>
>> On 5/23/2024 5:26 PM, Konstantin Ananyev wrote:
>>> From: Konstantin Ananyev <konstantin.anan...@huawei.com>
>>>
>>> ../drivers/net/ice/ice_rxtx.c:1871:29: warning: variable length array used
>>> [-Wvla]
>>>
>>> Here VLA is used as a temp array for mbufs that will be used as a split
>>> RX data buffers.
>>> As at any given time only one thread can do RX from particular queue,
>>> at rx_queue_setup() we can allocate extra space for that array, and then
>>> safely use it at RX fast-path.
>>>
>>
>> Is there a reason to allocate extra space in sw_ring and used some part
>> of it for split buffer, instead of allocating a new buffer for it?
>
> Less allocations - less points to fail, less checks to do.
> Again, having it close to sw_ring is probably a good thing too,
> possibly less pressure on MMU, etc. - even though I don't think it is really
> critical.
> But yes, it could be a separate rte_zmalloc(), even though
> I don't see good reason for that.
>
ack
>>
>>> Signed-off-by: Konstantin Ananyev <konstantin.anan...@huawei.com>
>>> ---
>>> drivers/net/ice/ice_rxtx.c | 18 ++++++++++++------
>>> drivers/net/ice/ice_rxtx.h | 2 ++
>>> 2 files changed, 14 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/drivers/net/ice/ice_rxtx.c b/drivers/net/ice/ice_rxtx.c
>>> index 95a2db3432..6395a3b50a 100644
>>> --- a/drivers/net/ice/ice_rxtx.c
>>> +++ b/drivers/net/ice/ice_rxtx.c
>>> @@ -1171,7 +1171,7 @@ ice_rx_queue_setup(struct rte_eth_dev *dev,
>>> struct ice_vsi *vsi = pf->main_vsi;
>>> struct ice_rx_queue *rxq;
>>> const struct rte_memzone *rz;
>>> - uint32_t ring_size;
>>> + uint32_t ring_size, tlen;
>>> uint16_t len;
>>> int use_def_burst_func = 1;
>>> uint64_t offloads;
>>> @@ -1279,9 +1279,14 @@ ice_rx_queue_setup(struct rte_eth_dev *dev,
>>> /* always reserve more for bulk alloc */
>>> len = (uint16_t)(nb_desc + ICE_RX_MAX_BURST);
>>>
>>> + /* allocate extra entries for SW split buffer */
>>> + tlen = ((rxq->offloads & RTE_ETH_RX_OFFLOAD_BUFFER_SPLIT) != 0) ?
>>> + rxq->rx_free_thresh : 0;
>>> + tlen += len;
>>> +
>>> /* Allocate the software ring. */
>>> rxq->sw_ring = rte_zmalloc_socket(NULL,
>>> - sizeof(struct ice_rx_entry) * len,
>>> + sizeof(struct ice_rx_entry) * tlen,
>>> RTE_CACHE_LINE_SIZE,
>>> socket_id);
>>> if (!rxq->sw_ring) {
>>> @@ -1290,6 +1295,8 @@ ice_rx_queue_setup(struct rte_eth_dev *dev,
>>> return -ENOMEM;
>>> }
>>>
>>> + rxq->sw_split_buf = (tlen == len) ? NULL : rxq->sw_ring + len;
>>> +
>>> ice_reset_rx_queue(rxq);
>>> rxq->q_set = true;
>>> dev->data->rx_queues[queue_idx] = rxq;
>>> @@ -1868,7 +1875,6 @@ ice_rx_alloc_bufs(struct ice_rx_queue *rxq)
>>> uint64_t dma_addr;
>>> int diag, diag_pay;
>>> uint64_t pay_addr;
>>> - struct rte_mbuf *mbufs_pay[rxq->rx_free_thresh];
>>>
>>> /* Allocate buffers in bulk */
>>> alloc_idx = (uint16_t)(rxq->rx_free_trigger -
>>> @@ -1883,7 +1889,7 @@ ice_rx_alloc_bufs(struct ice_rx_queue *rxq)
>>>
>>> if (rxq->offloads & RTE_ETH_RX_OFFLOAD_BUFFER_SPLIT) {
>>> diag_pay = rte_mempool_get_bulk(rxq->rxseg[1].mp,
>>> - (void *)mbufs_pay, rxq->rx_free_thresh);
>>> + (void *)rxq->sw_split_buf, rxq->rx_free_thresh);
>>>
>>
>> Are we allowed to call 'rte_mempool_get_bulk()' with NULL object_table,
>
> Nope.
>
>> as 'rxq->sw_split_buf' can be NULL?
>> Perhaps can allocate 'rxq->sw_split_buf' even buffer split offload is
>> not enabled?
>
> No, if (rxq->offloads & RTE_ETH_RX_OFFLOAD_BUFFER_SPLIT) !=0, then
> rxq->sw_split_buf should not be NULL.
> If it is, then there is a bug in my changes, though right now I don't see
> how it can happen: as in ice_rx_queue_setup() we always allocate space
> rxq->sw_split_buf when RTE_ETH_RX_OFFLOAD_BUFFER_SPLIT is set.
>
Ack, I see logical condition now.
This logic assumes 'rxq->rx_free_thresh' is not '0', although
practically this is true, technically can configure it 0 and crash the
application.
