> -----Original Message-----
> From: Feifei Wang <feifei.wa...@arm.com>
> Sent: Friday, June 25, 2021 5:40 PM
> To: Xing, Beilei <beilei.x...@intel.com>
> Cc: dev@dpdk.org; nd <n...@arm.com>; Ruifeng Wang
> <ruifeng.w...@arm.com>; nd <n...@arm.com>; nd <n...@arm.com>
> Subject: 回复: [PATCH v1 1/2] net/i40e: improve performance for scalar Tx
>
> <snip>
>
> > > int n = txq->tx_rs_thresh;
> > > int32_t i = 0, j = 0;
> > > const int32_t k = RTE_ALIGN_FLOOR(n, RTE_I40E_TX_MAX_FREE_BUF_SZ);
> > > const int32_t m = n % RTE_I40E_TX_MAX_FREE_BUF_SZ; struct rte_mbuf
> > > *free[RTE_I40E_TX_MAX_FREE_BUF_SZ];
> > >
> > > For FAST_FREE_MODE:
> > >
> > > if (k) {
> > > for (j = 0; j != k - RTE_I40E_TX_MAX_FREE_BUF_SZ;
> > > j += RTE_I40E_TX_MAX_FREE_BUF_SZ) {
> > > for (i = 0; i <RTE_I40E_TX_MAX_FREE_BUF_SZ; ++i, ++txep) {
> > > free[i] = txep->mbuf;
> > > txep->mbuf = NULL;
> > > }
> > > rte_mempool_put_bulk(free[0]->pool, (void **)free,
> > > RTE_I40E_TX_MAX_FREE_BUF_SZ);
> > > }
> > > }
> > >
> > > if (m) {
> > > for (i = 0; i < m; ++i, ++txep) {
> > > free[i] = txep->mbuf;
> > > txep->mbuf = NULL;
> > > }
> > > }
> > > rte_mempool_put_bulk(free[0]->pool, (void **)free, m); }
>
> > Seems no logical problem, but the code looks heavy due to for loops.
> > Did you run performance with this change when tx_rs_thresh >
> > RTE_I40E_TX_MAX_FREE_BUF_SZ?
>
> Sorry for my late rely. It takes me some time to do the test for this path and
> following is my test results:
>
> First, I come up with another way to solve this bug and compare it with
> "loop"(size of 'free' is 64).
> That is set the size of 'free' as a large constant. We know:
> tx_rs_thresh < ring_desc_size < I40E_MAX_RING_DESC(4096), so we can
> directly define as:
> struct rte_mbuf *free[RTE_I40E_TX_MAX_FREE_BUF_SZ];
>
> [1]Test Config:
> MRR Test: two porst & bi-directional flows & one core RX API:
> i40e_recv_pkts_bulk_alloc TX API: i40e_xmit_pkts_simple
> ring_descs_size: 1024
> Ring_I40E_TX_MAX_FREE_SZ: 64
>
> [2]Scheme:
> tx_rs_thresh = I40E_DEFAULT_TX_RSBIT_THRESH tx_free_thresh =
> I40E_DEFAULT_TX_FREE_THRESH tx_rs_thresh <= tx_free_thresh <
> nb_tx_desc So we change the value of 'tx_rs_thresh' by adjust
> I40E_DEFAULT_TX_RSBIT_THRESH
>
> [3]Test Results (performance improve):
> In X86:
> tx_rs_thresh/ tx_free_thresh 32/32 256/256
> 512/512
> 1.mempool_put(base) 0 0
> 0
> 2.mempool_put_bulk:loop +4.7% +5.6%
> +7.0%
> 3.mempool_put_bulk:large size for free +3.8% +2.3%
> -2.0%
> (free[I40E_MAX_RING_DESC])
>
> In Arm:
> N1SDP:
> tx_rs_thresh/ tx_free_thresh 32/32 256/256
> 512/512
> 1.mempool_put(base) 0 0
> 0
> 2.mempool_put_bulk:loop +7.9% +9.1%
> +2.9%
> 3.mempool_put_bulk:large size for free +7.1% +8.7%
> +3.4%
> (free[I40E_MAX_RING_DESC])
>
> Thunderx2:
> tx_rs_thresh/ tx_free_thresh 32/32 256/256
> 512/512
> 1.mempool_put(base) 0 0
> 0
> 2.mempool_put_bulk:loop +7.6% +10.5%
> +7.6%
> 3.mempool_put_bulk:large size for free +1.7% +18.4%
> +10.2%
> (free[I40E_MAX_RING_DESC])
>
> As a result, I feel maybe 'loop' is better and it seems not very heavy
> according to the test.
> What about your views and look forward to your reply.
> Thanks a lot.
Thanks for your patch and test.
It looks OK for me, please send V2.
