From: Bruce Richardson <bruce.richardson@intel.com>
To: Panu Matilainen <pmatilai@redhat.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH] eal: default to one memory channel if not specified
Date: Wed, 14 Oct 2015 14:05:00 +0100 [thread overview]
Message-ID: <20151014130500.GA4176@bricha3-MOBL3> (raw)
In-Reply-To: <561E44DB.9000307@redhat.com>
On Wed, Oct 14, 2015 at 03:04:43PM +0300, Panu Matilainen wrote:
> On 10/14/2015 02:45 PM, David Marchand wrote:
> >Hello Panu,
> >
> >On Wed, Oct 14, 2015 at 12:22 PM, Panu Matilainen <pmatilai@redhat.com
> ><mailto:pmatilai@redhat.com>> wrote:
> >
> > Obtaining the correct value, especially from a running system, can
> > be anything from difficult to plain impossible. Since the value is
> > merely an optimization and does not affect functionality otherwise,
> > its pointless to force such a guess on users initially, such things
> > belong to performance tuning phase.
> >
> > Signed-off-by: Panu Matilainen <pmatilai@redhat.com
> > <mailto:pmatilai@redhat.com>>
> > ---
> > lib/librte_eal/common/eal_common_options.c | 10 ++--------
> > 1 file changed, 2 insertions(+), 8 deletions(-)
> >
> > diff --git a/lib/librte_eal/common/eal_common_options.c
> > b/lib/librte_eal/common/eal_common_options.c
> > index 1f459ac..28f10a2 100644
> > --- a/lib/librte_eal/common/eal_common_options.c
> > +++ b/lib/librte_eal/common/eal_common_options.c
> > @@ -104,7 +104,7 @@ eal_reset_internal_config(struct internal_config
> > *internal_cfg)
> >
> > internal_cfg->memory = 0;
> > internal_cfg->force_nrank = 0;
> > - internal_cfg->force_nchannel = 0;
> > + internal_cfg->force_nchannel = 1;
> >
> >
> >Well, not too sure about this default value.
> >
> >- mempool code is already checking for the 0 value.
>
> Yeah, I noticed it already handles the zero case.
>
> >- API already tells for rte_memory_get_nchannel() :
> > * @return
> > * The number of memory channels on the system. The value is 0 if
> >unknown
> > * or not the same on all devices.
>
> ...but missed this one, and thought it'd be "safer" to return some non-zero
> value since callers might be expecting it to be a valid -n value.
>
> >
> >So, I would let it 0.
>
> Right, so just drop the default value, reword commit message accordingly and
> resend. Will do unless there are other objections.
>
> - Panu -
I was going to suggest using 4 as the default value, since the channel spreading
should work as designed on systems with either 1, 2 or 4 active channels.
However, given the zero-check inside the mempool code, maybe the default should
be set there instead of in the EAL. [I just don't think the default should be 1.]
Anyone else any other thoughts on this?
/Bruce
next prev parent reply other threads:[~2015-10-14 13:05 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-14 10:22 Panu Matilainen
2015-10-14 11:45 ` David Marchand
2015-10-14 12:04 ` Panu Matilainen
2015-10-14 13:05 ` Bruce Richardson [this message]
2015-10-15 11:49 ` [dpdk-dev] [PATCH 0/2] Provide reasonable default to -n Panu Matilainen
2015-10-15 11:49 ` [dpdk-dev] [PATCH 1/2] mempool: use a better default for number of memory channels Panu Matilainen
2015-10-15 11:49 ` [dpdk-dev] [PATCH 2/2] eal: make the -n argument optional Panu Matilainen
2015-10-15 12:03 ` [dpdk-dev] [PATCH 0/2] Provide reasonable default to -n David Marchand
2015-10-26 16:51 ` Thomas Monjalon
2015-10-15 12:10 ` Mcnamara, John
2015-10-15 12:36 ` Panu Matilainen
2015-10-15 13:12 ` Mcnamara, John
2015-10-26 16:50 ` Thomas Monjalon
2015-10-26 16:56 ` Thomas Monjalon
2015-10-27 7:19 ` Panu Matilainen
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