> -----Original Message----- > From: Alexander Duyck [mailto:alexander.du...@gmail.com] > Sent: Thursday, December 22, 2016 11:54 PM > To: maowenan > Cc: Stephen Hemminger; netdev@vger.kernel.org; jeffrey.t.kirs...@intel.com; > weiyongjun (A); Dingtianhong > Subject: Re: [PATCH] ethtool: add one ethtool option to set relax ordering > mode > > On Wed, Dec 21, 2016 at 5:39 PM, maowenan <maowe...@huawei.com> > wrote: > > > > > >> -----Original Message----- > >> From: Stephen Hemminger [mailto:step...@networkplumber.org] > >> Sent: Thursday, December 22, 2016 9:28 AM > >> To: maowenan > >> Cc: netdev@vger.kernel.org; jeffrey.t.kirs...@intel.com > >> Subject: Re: [PATCH] ethtool: add one ethtool option to set relax > >> ordering mode > >> > >> On Thu, 8 Dec 2016 14:51:38 +0800 > >> Mao Wenan <maowe...@huawei.com> wrote: > >> > >> > This patch provides one way to set/unset IXGBE NIC TX and RX relax > >> > ordering mode, which can be set by ethtool. > >> > Relax ordering is one mode of 82599 NIC, to enable this mode can > >> > enhance the performance for some cpu architecure. > >> > >> Then it should be done by CPU architecture specific quirks > >> (preferably in PCI > >> layer) so that all users get the option without having to do manual > intervention. > >> > >> > example: > >> > ethtool -s enp1s0f0 relaxorder off > >> > ethtool -s enp1s0f0 relaxorder on > >> > >> Doing it via ethtool is a developer API (for testing) not something > >> that makes sense in production. > > > > > > This feature is not mandatory for all users, acturally relax ordering > > default configuration of 82599 is 'disable', So this patch gives one way to > enable relax ordering to be selected in some performance condition. > > That isn't quite true. The default for Sparc systems is to have it enabled. > > Really this is something that is platform specific. I agree with Stephen > that it > would work better if this was handled as a series of platform specific quirks > handled at something like the PCI layer rather than be a switch the user can > toggle on and off. > > With that being said there are changes being made that should help to improve > the situation. Specifically I am looking at adding support for the > DMA_ATTR_WEAK_ORDERING which may also allow us to identify cases where > you might be able to specify the DMA behavior via the DMA mapping instead of > having to make the final decision in the device itself. > > - Alex
Yes, Sparc is a special case. From the NIC driver point of view, It is no need for some ARCHs to do particular operation and compiling branch, ethtool is a flexible method for user to make decision whether on|off this feature. I think Jeff as maintainer of 82599 has some comments about this. -Wenan
