[dpdk-dev] 回复: [PATCH v1 1/2] net/i40e: improve performance for scalar Tx

[Feifei Wang <Feifei.Wang2@arm.com>]

> -----邮件原件-----
> 发件人: Xing, Beilei <beilei.xing@intel.com>
> 发送时间: 2021年6月28日 10:27
> 收件人: Feifei Wang <Feifei.Wang2@arm.com>
> 抄送: dev@dpdk.org; nd <nd@arm.com>; Ruifeng Wang
> <Ruifeng.Wang@arm.com>; nd <nd@arm.com>; nd <nd@arm.com>
> 主题: RE: [PATCH v1 1/2] net/i40e: improve performance for scalar Tx
> 
> 
> 
> > -----Original Message-----
> > From: Feifei Wang <Feifei.Wang2@arm.com>
> > Sent: Friday, June 25, 2021 5:40 PM
> > To: Xing, Beilei <beilei.xing@intel.com>
> > Cc: dev@dpdk.org; nd <nd@arm.com>; Ruifeng Wang
> > <Ruifeng.Wang@arm.com>; nd <nd@arm.com>; nd <nd@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.
Thanks for the reviewing, I will update the V2 version.