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From: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>
To: Stephen Hemminger <stephen@networkplumber.org>,
	"Xie, Huawei" <huawei.xie@intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>, "dprovan@bivio.net" <dprovan@bivio.net>
Subject: Re: [dpdk-dev] [PATCH v3 1/2] mbuf: provide rte_pktmbuf_alloc_bulk	API
Date: Wed, 23 Dec 2015 18:49:22 +0000	[thread overview]
Message-ID: <2601191342CEEE43887BDE71AB97725836AD8261@irsmsx105.ger.corp.intel.com> (raw)
In-Reply-To: <20151223103744.28551da7@xeon-e3>



> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Stephen Hemminger
> Sent: Wednesday, December 23, 2015 6:38 PM
> To: Xie, Huawei
> Cc: dev@dpdk.org; dprovan@bivio.net
> Subject: Re: [dpdk-dev] [PATCH v3 1/2] mbuf: provide rte_pktmbuf_alloc_bulk API
> 
> On Wed, 23 Dec 2015 00:17:53 +0800
> Huawei Xie <huawei.xie@intel.com> wrote:
> 
> > +
> > +	rc = rte_mempool_get_bulk(pool, (void **)mbufs, count);
> > +	if (unlikely(rc))
> > +		return rc;
> > +
> > +	switch (count % 4) {
> > +	case 0: while (idx != count) {
> > +			RTE_MBUF_ASSERT(rte_mbuf_refcnt_read(mbufs[idx]) == 0);
> > +			rte_mbuf_refcnt_set(mbufs[idx], 1);
> > +			rte_pktmbuf_reset(mbufs[idx]);
> > +			idx++;
> > +	case 3:
> > +			RTE_MBUF_ASSERT(rte_mbuf_refcnt_read(mbufs[idx]) == 0);
> > +			rte_mbuf_refcnt_set(mbufs[idx], 1);
> > +			rte_pktmbuf_reset(mbufs[idx]);
> > +			idx++;
> > +	case 2:
> > +			RTE_MBUF_ASSERT(rte_mbuf_refcnt_read(mbufs[idx]) == 0);
> > +			rte_mbuf_refcnt_set(mbufs[idx], 1);
> > +			rte_pktmbuf_reset(mbufs[idx]);
> > +			idx++;
> > +	case 1:
> > +			RTE_MBUF_ASSERT(rte_mbuf_refcnt_read(mbufs[idx]) == 0);
> > +			rte_mbuf_refcnt_set(mbufs[idx], 1);
> > +			rte_pktmbuf_reset(mbufs[idx]);
> > +			idx++;
> > +	}
> > +	}
> > +	return 0;
> > +}
> 
> Since function will not work if count can not be 0 (otherwise rte_mempool_get_bulk will fail),

As I understand, rte_mempool_get_bulk() will work correctly and return 0, if count==0.
That's why Huawei prefers while() {}, instead of do {} while() - to avoid extra check for
(count != 0) at the start. 
Konstantin


> why not:
> 	1. Document that assumption
> 	2. Use that assumption to speed up code.
> 
> 
> 
> 	switch(count % 4) {
> 		do {
> 			case 0:
> 			...
> 			case 1:
> 			...
> 		} while (idx != count);
> 	}
> 
> Also you really need to add a big block comment about this loop, to explain
> what it does and why.

  reply	other threads:[~2015-12-23 18:49 UTC|newest]

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-12-13 23:35 [dpdk-dev] [PATCH 0/2] provide rte_pktmbuf_alloc_bulk API and call it in vhost dequeue Huawei Xie
2015-12-13 23:35 ` [dpdk-dev] [PATCH 1/2] mbuf: provide rte_pktmbuf_alloc_bulk API Huawei Xie
2015-12-13 23:35 ` [dpdk-dev] [PATCH 2/2] vhost: call rte_pktmbuf_alloc_bulk in vhost dequeue Huawei Xie
2015-12-14  1:14 ` [dpdk-dev] [PATCH v2 0/2] provide rte_pktmbuf_alloc_bulk API and call it " Huawei Xie
2015-12-14  1:14   ` [dpdk-dev] [PATCH v2 1/2] mbuf: provide rte_pktmbuf_alloc_bulk API Huawei Xie
2015-12-17  6:41     ` Yuanhan Liu
2015-12-17 15:42       ` Ananyev, Konstantin
2015-12-18  2:17         ` Yuanhan Liu
2015-12-18  5:01     ` Stephen Hemminger
2015-12-18  5:21       ` Yuanhan Liu
2015-12-18  7:10       ` Xie, Huawei
2015-12-18 10:44       ` Ananyev, Konstantin
2015-12-18 17:32         ` Stephen Hemminger
2015-12-18 19:27           ` Wiles, Keith
2015-12-21 15:21             ` Xie, Huawei
2015-12-21 17:20               ` Wiles, Keith
2015-12-21 21:30                 ` Thomas Monjalon
2015-12-22  1:58                   ` Xie, Huawei
2015-12-21 22:34               ` Don Provan
2015-12-21 12:25           ` Xie, Huawei
2015-12-14  1:14   ` [dpdk-dev] [PATCH v2 2/2] vhost: call rte_pktmbuf_alloc_bulk in vhost dequeue Huawei Xie
2015-12-17  6:41     ` Yuanhan Liu
2015-12-22 16:17   ` [dpdk-dev] [PATCH v3 0/2] provide rte_pktmbuf_alloc_bulk API and call it " Huawei Xie
2015-12-22 16:17     ` [dpdk-dev] [PATCH v3 1/2] mbuf: provide rte_pktmbuf_alloc_bulk API Huawei Xie
2015-12-23 18:37       ` Stephen Hemminger
2015-12-23 18:49         ` Ananyev, Konstantin [this message]
2015-12-24  1:33           ` Xie, Huawei
2015-12-22 16:17     ` [dpdk-dev] [PATCH v3 2/2] vhost: call rte_pktmbuf_alloc_bulk in vhost dequeue Huawei Xie
2015-12-23 11:22       ` linhaifeng
2015-12-23 11:39         ` Xie, Huawei
2015-12-22 23:05 ` [dpdk-dev] [PATCH v4 0/2] provide rte_pktmbuf_alloc_bulk API and call it " Huawei Xie
2015-12-22 23:05   ` [dpdk-dev] [PATCH v4 1/2] mbuf: provide rte_pktmbuf_alloc_bulk API Huawei Xie
2015-12-22 23:05   ` [dpdk-dev] [PATCH v4 2/2] vhost: call rte_pktmbuf_alloc_bulk in vhost dequeue Huawei Xie
2015-12-27 16:38 ` [dpdk-dev] [PATCH v5 0/2] provide rte_pktmbuf_alloc_bulk API and call it " Huawei Xie
2015-12-27 16:38   ` [dpdk-dev] [PATCH v5 1/2] mbuf: provide rte_pktmbuf_alloc_bulk API Huawei Xie
2015-12-27 16:38   ` [dpdk-dev] [PATCH v5 2/2] vhost: call rte_pktmbuf_alloc_bulk in vhost dequeue Huawei Xie
2016-01-26 17:03 ` [dpdk-dev] [PATCH v6 0/2] provide rte_pktmbuf_alloc_bulk API and call it " Huawei Xie
2016-01-26 17:03   ` [dpdk-dev] [PATCH v6 1/2] mbuf: provide rte_pktmbuf_alloc_bulk API Huawei Xie
2016-01-27 13:56     ` Panu Matilainen
2016-02-03 17:23       ` Olivier MATZ
2016-02-22 14:49         ` Xie, Huawei
2016-02-23  5:35           ` Xie, Huawei
2016-02-24 12:11             ` Panu Matilainen
2016-02-24 13:23               ` Ananyev, Konstantin
2016-02-26  7:39                 ` Xie, Huawei
2016-02-26  8:45                   ` Olivier MATZ
2016-02-29 10:51                 ` Panu Matilainen
2016-02-29 16:14                   ` Thomas Monjalon
2016-02-26  8:55             ` Olivier MATZ
2016-02-26  9:07               ` Xie, Huawei
2016-02-26  9:18                 ` Olivier MATZ
2016-01-26 17:03   ` [dpdk-dev] [PATCH v6 2/2] vhost: call rte_pktmbuf_alloc_bulk in vhost dequeue Huawei Xie
2016-02-28 12:44 ` [dpdk-dev] [PATCH v7] mbuf: provide rte_pktmbuf_alloc_bulk API Huawei Xie
2016-02-29 16:27   ` Thomas Monjalon

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