From: Stephen Hemminger <stephen@networkplumber.org>
To: Bruce Richardson <bruce.richardson@intel.com>
Cc: dev@dpdk.org, Stephen Hemminger <shemming@brocade.com>
Subject: Re: [PATCH 2/2] mbuf: make sure userdata is initialized
Date: Fri, 10 Jul 2015 08:43:56 -0700 [thread overview]
Message-ID: <20150710084356.37d22b65@urahara> (raw)
In-Reply-To: <20150710093217.GB10556@bricha3-MOBL3>
On Fri, 10 Jul 2015 10:32:17 +0100
Bruce Richardson <bruce.richardson@intel.com> wrote:
> On Thu, Jul 09, 2015 at 04:37:48PM -0700, Stephen Hemminger wrote:
> > From: Stephen Hemminger <shemming@brocade.com>
> >
> > For applications that use m->userdata the initialization can
> > be a signficant (10%) performance penalty.
> >
> > Rather than taking the cache penalty of initializing userdata
> > in the receive handling, do it in the place where mbuf is
> > already cache hot and being setup.
>
> Should the management of the userdata field not be the responsibility of the
> app itself, rather than having the PMD manage it? If the PMD does manage the
> userdata field, I would suggest taking the approach of having the field cleared
> by the mbuf library on free, rather than on RX.
The problem with that is m->userdata is that when the application
gets the mbuf, touching the userdata field causes false cache
sharing and we see a significant performance drop. Internally the
userdata field is only used for few special cases and 0/NULL
is used to indicate that no metadata is present.
next prev parent reply other threads:[~2015-07-10 15:43 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-09 23:37 [PATCH 0/2] mbuf: improvements Stephen Hemminger
2015-07-09 23:37 ` [PATCH 1/2] mbuf: Add rte_pktmbuf_copy Stephen Hemminger
2015-07-15 10:14 ` Olivier MATZ
2016-01-22 13:40 ` Mrzyglod, DanielX T
2016-01-22 17:33 ` Stephen Hemminger
2016-03-18 17:03 ` Pattan, Reshma
2016-03-18 17:40 ` Stephen Hemminger
2016-02-03 17:23 ` Olivier MATZ
[not found] ` <ccbdb829556f4423b009aff93f27c93b@BRMWP-EXMB11.corp.brocade.com>
2016-02-04 0:49 ` Stephen Hemminger
2015-07-09 23:37 ` [PATCH 2/2] mbuf: make sure userdata is initialized Stephen Hemminger
2015-07-10 9:32 ` Bruce Richardson
2015-07-10 15:43 ` Stephen Hemminger [this message]
2015-07-15 10:10 ` Olivier MATZ
2016-02-03 17:23 ` Olivier MATZ
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