回复: [PATCH v2] net/i40e: reduce redundant store operation

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

> -----邮件原件-----
> 发件人: Zhang, Qi Z <qi.z.zhang@intel.com>
> 发送时间: Wednesday, January 26, 2022 10:28 PM
> 收件人: Feifei Wang <Feifei.Wang2@arm.com>; Xing, Beilei
> <beilei.xing@intel.com>
> 抄送: dev@dpdk.org; Wang, Haiyue <haiyue.wang@intel.com>; nd
> <nd@arm.com>; Ruifeng Wang <Ruifeng.Wang@arm.com>
> 主题: RE: [PATCH v2] net/i40e: reduce redundant store operation
> 
> 
> 
> > -----Original Message-----
> > From: Feifei Wang <feifei.wang2@arm.com>
> > Sent: Tuesday, December 21, 2021 4:11 PM
> > To: Xing, Beilei <beilei.xing@intel.com>
> > Cc: dev@dpdk.org; Wang, Haiyue <haiyue.wang@intel.com>; nd@arm.com;
> > Feifei Wang <feifei.wang2@arm.com>; Ruifeng Wang
> > <ruifeng.wang@arm.com>
> > Subject: [PATCH v2] net/i40e: reduce redundant store operation
> >
> > For free buffer operation in i40e vector path, it is unnecessary to store
> 'NULL'
> > into txep.mbuf. This is because when putting mbuf into Tx queue,
> > tx_tail is the sentinel. And when doing tx_free, tx_next_dd is the
> > sentinel. In all processes, mbuf==NULL is not a condition in check.
> > Thus reset of mbuf is unnecessary and can be omitted.
> >
> > Signed-off-by: Feifei Wang <feifei.wang2@arm.com>
> > Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> > ---
> >
> > v2: remove the change for scalar path due to scalar path needs to
> > check whether the mbuf is 'NULL' to release and clean up (Haiyue)
> >
> >  drivers/net/i40e/i40e_rxtx_vec_common.h | 1 -
> >  1 file changed, 1 deletion(-)
> >
> > diff --git a/drivers/net/i40e/i40e_rxtx_vec_common.h
> > b/drivers/net/i40e/i40e_rxtx_vec_common.h
> > index f9a7f46550..26deb59fc4 100644
> > --- a/drivers/net/i40e/i40e_rxtx_vec_common.h
> > +++ b/drivers/net/i40e/i40e_rxtx_vec_common.h
> > @@ -103,7 +103,6 @@ i40e_tx_free_bufs(struct i40e_tx_queue *txq)
> >  	if (txq->offloads & RTE_ETH_TX_OFFLOAD_MBUF_FAST_FREE) {
> >  		for (i = 0; i < n; i++) {
> >  			free[i] = txep[i].mbuf;
> > -			txep[i].mbuf = NULL;
> 
> I will suggest to still add some comment here just for explaining, this may help
> to avoid unnecessary suspect when someone reading or debug on these code
> 😊
> 
Thanks for your comments. Agree with this, and I will add the comment to
explain why this store operation is unnecessary here.
> 
> >  		}
> >  		rte_mempool_put_bulk(free[0]->pool, (void **)free, n);
> >  		goto done;
> > --
> > 2.25.1