From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Marchand Subject: Re: i40e: Steps and required configurations of how to achieve the best performance! Date: Wed, 17 Sep 2014 16:03:05 +0200 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Cc: "dev-VfR2kkLFssw@public.gmane.org" To: "Zhang, Helin" Return-path: In-Reply-To: List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces-VfR2kkLFssw@public.gmane.org Sender: "dev" On Wed, Sep 17, 2014 at 10:50 AM, Zhang, Helin wrote: > For the =E2=80=98extended tag=E2=80=99, it was defined in PCIe spec, but= actually not > all BIOS implements it. Enabling it in BIOS or at runtime are two choices > of doing the same thing. I don=E2=80=99t think it can be configured per P= CI device > in BIOS, so we don=E2=80=99t need to do that per PCI device in DPDK. Righ= t? > Actually we don=E2=80=99t want to touch PCIe settings in DPDK code, that= =E2=80=99s why we > want to let BIOS config as it is by default. If no better choice, we can = do > it in DPDK by changing configurations. > - Ok, then if we can make a runtime decision (at dpdk level), there is no need for bios configuration and there is no need for a build option. Why don't we get rid of this option ? As far as the per-device runtime configuration is concerned, I want to make sure this pci configuration will not break other "igb_uio" pci devices. If Intel can tell for sure this won't break other devices, then fine, we can go and enable this for all "igb_uio" pci devices. - By the way, there is also the CONFIG_MAX_READ_REQUEST_SIZE option that seems to be disabled (or at least its value 0 seems to tell so). What is its purpose ? > > For =E2=80=98CONFIG_RTE_LIBRTE_I40E_16BYTE_RX_DESC=3Dn=E2=80=99 by defaul= t, we want to > support 32 bytes rx descriptors by default. Two reasons: > > One is 32 bytes rx descriptors can provide more powerful features, and > more offload features. > > The other is Linux PF host use 32 bytes rx descriptor by default which > might not able to be changed, to support Linux PF host, it would be bette= r > to use 32 bytes rx descriptors in DPDK VF by default. > Ok, good to know. Thanks. --=20 David Marchand