From mboxrd@z Thu Jan  1 00:00:00 1970
From: Thomas Monjalon <thomas@monjalon.net>
Subject: Re: [dpdk-stable] AVX512 bug on SkyLake
Date: Mon, 12 Nov 2018 10:21:56 +0100
Message-ID: <1966988.vJfdJNsEgr@xps>
References: <20181023212318.43082-1-yskoh@mellanox.com>
 <14171327.rkP5k0YJWv@xps>
 <CAATJJ0JmoMup+LL2-4Z8AJ29tzXFO+97_OKwW4M4NRR4EKVjFg@mail.gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7Bit
Cc: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>,
 Ferruh Yigit <ferruh.yigit@intel.com>,
 Bruce Richardson <bruce.richardson@intel.com>, stable@dpdk.org,
 keith.wiles@intel.com, yskoh@mellanox.com, dev <dev@dpdk.org>,
 Shahaf Shuler <shahafs@mellanox.com>, anatoly.burakov@intel.com,
 justin.parus@microsoft.com, David Coronel <david.coronel@canonical.com>,
 Josh Powers <josh.powers@canonical.com>,
 Jay Vosburgh <jay.vosburgh@canonical.com>,
 Dan Streetman <dan.streetman@canonical.com>
To: Christian Ehrhardt <christian.ehrhardt@canonical.com>
Return-path: <dev-bounces@dpdk.org>
In-Reply-To: <CAATJJ0JmoMup+LL2-4Z8AJ29tzXFO+97_OKwW4M4NRR4EKVjFg@mail.gmail.com>
List-Id: DPDK patches and discussions <dev.dpdk.org>
List-Unsubscribe: <https://mails.dpdk.org/options/dev>,
 <mailto:dev-request@dpdk.org?subject=unsubscribe>
List-Archive: <http://mails.dpdk.org/archives/dev/>
List-Post: <mailto:dev@dpdk.org>
List-Help: <mailto:dev-request@dpdk.org?subject=help>
List-Subscribe: <https://mails.dpdk.org/listinfo/dev>,
 <mailto:dev-request@dpdk.org?subject=subscribe>
Errors-To: dev-bounces@dpdk.org
Sender: "dev" <dev-bounces@dpdk.org>

12/11/2018 10:09, Christian Ehrhardt:
> > -    vmovdqu8 xmm0,XMMWORD PTR [rax*8+0x6]
> > +    vmovdqu xmm0,XMMWORD PTR [rax*8+0x60]
> >      vinserti128 ymm0,ymm0,XMMWORD PTR [rax*8+0x70],0x1
> >      vmovups XMMWORD PTR [rsi+0x60],xmm0
> >      vextracti128 XMMWORD PTR [rsi+0x70],ymm0,0x1
> >
> > > Not sure what causing compiler behaves that way.
> > > BTW, looking though testpmd objdump output - it seems that only mlx5 driver
> > > exhibits such problem (I didn't enable mlx4 actually, probably same problem here).
> > > Which looks a bit weird to me.
> >
> > Yes it's weird. I don't see how the mlx5 code could influence
> > the compiler to generate this bad code in AVX512 mode.
> 
> Thomas you have all this set up, do you have any chance to test this
> on the GCC's in Ubuntu 18.10 and 19.04
> If easy I'd love to see results wit hgcc-7 & gcc-8 as in Ubuntu 19.04
> (current -dev).
> If the above is too hard, at least could you try the gcc-8 in Bionic
> is 8.2.0-1ubuntu2~18.04 that is rather close.

I already tested updated GCC 7 and 8 (it is the same result):
	https://bugs.dpdk.org/show_bug.cgi?id=97#c18

Versions are:
	gcc-7 (Ubuntu 7.3.0-27ubuntu1~18.04) 7.3.0
	gcc-8 (Ubuntu 8.2.0-1ubuntu2~18.04) 8.2.0

> If you could share the simplified build options that you need to
> reproduce that would help (at least me) - thanks in advance

You just need to compile mlx5, nothing special.