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From: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>
To: "Richardson, Bruce" <bruce.richardson@intel.com>,
	Morten Brørup <mb@smartsharesystems.com>
Cc: Thomas Monjalon <thomas@monjalon.net>,
	"dev@dpdk.org" <dev@dpdk.org>,
	"david.marchand@redhat.com" <david.marchand@redhat.com>,
	"Yigit, Ferruh" <ferruh.yigit@intel.com>,
	"olivier.matz@6wind.com" <olivier.matz@6wind.com>,
	"andrew.rybchenko@oktetlabs.ru" <andrew.rybchenko@oktetlabs.ru>,
	"viacheslavo@nvidia.com" <viacheslavo@nvidia.com>,
	"ajit.khaparde@broadcom.com" <ajit.khaparde@broadcom.com>,
	"jerinj@marvell.com" <jerinj@marvell.com>,
	"hemant.agrawal@nxp.com" <hemant.agrawal@nxp.com>,
	Ray Kinsella <mdr@ashroe.eu>, Neil Horman <nhorman@tuxdriver.com>,
	Nithin Dabilpuram <ndabilpuram@marvell.com>,
	"Kiran Kumar K" <kirankumark@marvell.com>,
	"techboard@dpdk.org" <techboard@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH 1/1] mbuf: move pool pointer in first half
Date: Mon, 9 Nov 2020 10:33:41 +0000
Message-ID: <DM6PR11MB3308005609F8FFC3A39F27B39AEA0@DM6PR11MB3308.namprd11.prod.outlook.com> (raw)
In-Reply-To: <20201109100838.GC831@bricha3-MOBL.ger.corp.intel.com>



> On Sat, Nov 07, 2020 at 07:57:05PM +0100, Morten Brørup wrote:
> > > From: Thomas Monjalon [mailto:thomas@monjalon.net]
> > > Sent: Saturday, November 7, 2020 4:53 PM
> > >
> > > The mempool pointer in the mbuf struct is moved
> > > from the second to the first half.
> > > It should increase performance on most systems having 64-byte cache line,
> > > i.e. mbuf is split in two cache lines.
> >
> > Perhaps with the #define DEV_TX_OFFLOAD_MBUF_FAST_FREE mentioned by Konstantin, it might be better moving m->next instead, at
> least for applications with the opportunity to set this flag (e.g. applications with only one mbuf pool).
> >
> > Unfortunately, the information about the DEV_TX_OFFLOAD_MBUF_FAST_FREE flag came to light after the techboard meeting, and I
> don't have any benchmarks to support this suggestion, so I guess it's hard to change the techboard's decision to move the pool pointer.
> >
> 
> The thing with FAST_FREE is that it doesn't just indicate that there is
> only one mbuf pool, but rather that none of the packets are chained mbufs
> either.

Hmm, wonder where such assumption comes from?
There is nothing about forbidding chained mbufs in rte_ethdev.h right now:
#define DEV_TX_OFFLOAD_MBUF_FAST_FREE   0x00010000
/**< Device supports optimization for fast release of mbufs.
 *   When set application must guarantee that per-queue all mbufs comes from
 *   the same mempool and has refcnt = 1.
 */ 

> Therefore, the flag applies equally to both next and pool pointers
> for optimization. [And the flag should perhaps be two flags!]
> 

I think what Morten means here:
For FAST_FREE PMD can store pool pointer somewhere in its queue metadata
and doesn't need to read it from the mbuf.
So if we move next to first line - mbuf_free code-path for FAST_FREE case can
avoid touching  second cache line in the mbuf. 




  parent reply	other threads:[~2020-11-09 10:33 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-07 15:53 Thomas Monjalon
2020-11-07 17:12 ` Jerin Jacob
2020-11-07 18:39   ` Thomas Monjalon
2020-11-07 19:05     ` Jerin Jacob
2020-11-07 20:33       ` Thomas Monjalon
2020-11-09  5:18         ` Jerin Jacob
2020-11-09  8:04           ` Thomas Monjalon
2020-11-09  8:27             ` Jerin Jacob
2020-11-09  9:47               ` Bruce Richardson
2020-11-09 12:01                 ` Jerin Jacob
2020-11-09 12:59                   ` Thomas Monjalon
2020-11-09 13:35                     ` Jerin Jacob
2020-11-09 14:02                       ` Thomas Monjalon
2020-11-09 14:08                         ` Jerin Jacob
2020-11-09 14:42                           ` Thomas Monjalon
2020-11-09 14:53                             ` Jerin Jacob
2020-11-09  8:16           ` Morten Brørup
2020-11-09 10:06             ` [dpdk-dev] [dpdk-techboard] " Bruce Richardson
2020-11-09 10:21               ` Morten Brørup
2020-11-09 18:04                 ` Stephen Hemminger
2020-11-10  7:15                   ` Morten Brørup
2020-11-07 18:57 ` [dpdk-dev] " Morten Brørup
2020-11-09 10:08   ` Bruce Richardson
2020-11-09 10:30     ` Morten Brørup
2020-11-09 10:33     ` Ananyev, Konstantin [this message]
2020-11-09 10:36       ` Bruce Richardson
2020-11-09 11:24       ` Ananyev, Konstantin
2020-11-09 21:29 ` [dpdk-dev] [PATCH v2 0/2] move mbuf pool pointer Thomas Monjalon
2020-11-09 21:29   ` [dpdk-dev] [PATCH v2 1/2] drivers: disable OCTEON TX2 in 32-bit build Thomas Monjalon
2020-11-10 18:05     ` Jerin Jacob
2020-11-09 21:29   ` [dpdk-dev] [PATCH v2 2/2] mbuf: move pool pointer in first half Thomas Monjalon
2020-11-10 10:05     ` Morten Brørup
2020-11-10 10:44       ` Thomas Monjalon
2020-11-10 16:25     ` Olivier Matz
2020-11-10 18:06       ` Jerin Jacob
2020-11-12 14:39         ` Thomas Monjalon
2020-11-10 18:08       ` Stephen Hemminger

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