From: Jan Viktorin <viktorin@rehivetech.com>
To: Thomas Monjalon <thomas.monjalon@6wind.com>
Cc: Jerin Jacob <jerin.jacob@caviumnetworks.com>,
Tomasz Kulasek <tomaszx.kulasek@intel.com>,
dev@dpdk.org, jianbo.liu@linaro.org
Subject: Re: [dpdk-dev] [PATCH v5] examples/l3fwd: em path performance fix
Date: Fri, 18 Mar 2016 12:56:50 +0100 [thread overview]
Message-ID: <20160318125650.7469a086@pcviktorin.fit.vutbr.cz> (raw)
In-Reply-To: <1734050.PspUeD4iGQ@xps13>
Hello Thomas, Jerin, Tomasz, all...
On Fri, 18 Mar 2016 12:00:24 +0100
Thomas Monjalon <thomas.monjalon@6wind.com> wrote:
> 2016-03-18 16:22, Jerin Jacob:
> > On Fri, Mar 18, 2016 at 11:04:49AM +0100, Thomas Monjalon wrote:
> > > 2016-03-18 10:52, Tomasz Kulasek:
> > > > +#if !defined(NO_HASH_MULTI_LOOKUP) && defined(__ARM_NEON)
> > >
> > > I think we should use CONFIG_RTE_ARCH_ARM_NEON here.
> > > Any ARM maintainer to confirm?
> >
> > __ARM_NEON should work existing GCC, but it is better to use
> > RTE_MACHINE_CPUFLAG_NEON as
> > -it has been generated by probing the compiler capabilities.
> > -it's future-proof solution to support clang or other gcc versions in
> > future
>
> I agree to use RTE_MACHINE_CPUFLAG_NEON.
>
> I just don't understand why CONFIG_RTE_ARCH_ARM_NEON has been introduced.
> It seems to be used to disable NEON on ARMv7:
This is true. You should be able to disable the NEON-specific code if it
is unwanted. Eg., the memcpy operations are not always faster with NEON.
But...
$ git grep ARM_NEON
...
lib/librte_eal/common/include/arch/arm/rte_memcpy_32.h:45:#ifdef __ARM_NEON_FP
lib/librte_eal/common/include/arch/arm/rte_memcpy_32.h:328:#endif /* __ARM_NEON_FP */
...
From this point of view, this is wrong and should be fixed to check
a different constant.
> ifeq ($(CONFIG_RTE_ARCH_ARM_NEON),y)
> MACHINE_CFLAGS += -mfpu=neon
> endif
However, there is another possible way of understanding these options.
We can (well, unlikely and I am about to say 'never') have an ARM
processor without NEON. This cannot be detected by gcc as it does not
know the target processor... So from my point of view:
* CONFIG_RTE_ARCH_ARM_NEON says "my CPU does (not) support NEON" or "I
want to enable/disable NEON" while
* RTE_MACHINE_CPUFLAG_NEON says, the _compiler_ supports NEON
I'll send a patch trying to solve this.
Regards
Jan
next prev parent reply other threads:[~2016-03-18 11:56 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-03 17:23 [dpdk-dev] [PATCH] " Tomasz Kulasek
2016-03-07 6:19 ` Xu, Qian Q
2016-03-08 12:58 ` [dpdk-dev] [PATCH v2] " Tomasz Kulasek
2016-03-11 11:14 ` Thomas Monjalon
2016-03-11 12:28 ` Kulasek, TomaszX
2016-03-11 12:10 ` [dpdk-dev] [PATCH v3] " Tomasz Kulasek
2016-03-11 16:23 ` Thomas Monjalon
2016-03-11 17:48 ` Kulasek, TomaszX
2016-03-15 14:31 ` Kulasek, TomaszX
2016-03-15 14:49 ` Thomas Monjalon
2016-03-15 16:06 ` Kulasek, TomaszX
2016-03-15 19:42 ` [dpdk-dev] Odp.: " Czekaj, Maciej
2016-03-18 9:36 ` [dpdk-dev] [PATCH v4] " Tomasz Kulasek
2016-03-18 9:43 ` Kulasek, TomaszX
2016-03-18 9:52 ` [dpdk-dev] [PATCH v5] " Tomasz Kulasek
2016-03-18 10:04 ` Thomas Monjalon
2016-03-18 10:52 ` Jerin Jacob
2016-03-18 11:00 ` Thomas Monjalon
2016-03-18 11:16 ` [dpdk-dev] [PATCH] examples/l3fwd: prefer probed NEON flag to ARM gcc flag Thomas Monjalon
2016-03-18 11:20 ` [dpdk-dev] [PATCH v2] " Thomas Monjalon
2016-03-18 11:56 ` Jan Viktorin [this message]
2016-03-18 12:45 ` [dpdk-dev] [PATCH v5] examples/l3fwd: em path performance fix Kulasek, TomaszX
2016-03-18 12:50 ` Jan Viktorin
2016-03-18 13:31 ` [dpdk-dev] [PATCH v6] " Tomasz Kulasek
2016-03-21 11:57 ` Thomas Monjalon
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20160318125650.7469a086@pcviktorin.fit.vutbr.cz \
--to=viktorin@rehivetech.com \
--cc=dev@dpdk.org \
--cc=jerin.jacob@caviumnetworks.com \
--cc=jianbo.liu@linaro.org \
--cc=thomas.monjalon@6wind.com \
--cc=tomaszx.kulasek@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).