From mboxrd@z Thu Jan 1 00:00:00 1970 From: okaya@codeaurora.org Subject: Re: [PATCH v7 0/7] netdev: intel: Eliminate duplicate barriers on weakly-ordered archs Date: Fri, 23 Mar 2018 22:34:46 -0400 Message-ID: <862cdbeafb9cfd272a426b010943ffc5@codeaurora.org> References: <1521831180-25014-1-git-send-email-okaya@codeaurora.org> <1521849496.15055.16.camel@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1521849496.15055.16.camel@intel.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Jeff Kirsher Cc: sulrich@codeaurora.org, Netdev , Timur Tabi , Alexander Duyck , intel-wired-lan , linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org List-Id: linux-arm-msm@vger.kernel.org On 2018-03-23 19:58, Jeff Kirsher wrote: > On Fri, 2018-03-23 at 14:53 -0700, Alexander Duyck wrote: >> On Fri, Mar 23, 2018 at 11:52 AM, Sinan Kaya >> wrote: >> > Code includes wmb() followed by writel() in multiple places. writel() >> > already has a barrier on some architectures like arm64. >> > >> > This ends up CPU observing two barriers back to back before executing >> > the >> > register write. >> > >> > Since code already has an explicit barrier call, changing writel() to >> > writel_relaxed(). >> > >> > I did a regex search for wmb() followed by writel() in each drivers >> > directory. >> > I scrubbed the ones I care about in this series. >> > >> > I considered "ease of change", "popular usage" and "performance >> > critical >> > path" as the determining criteria for my filtering. >> > >> > We used relaxed API heavily on ARM for a long time but >> > it did not exist on other architectures. For this reason, relaxed >> > architectures have been paying double penalty in order to use the >> > common >> > drivers. >> > >> > Now that relaxed API is present on all architectures, we can go and >> > scrub >> > all drivers to see what needs to change and what can remain. >> > >> > We start with mostly used ones and hope to increase the coverage over >> > time. >> > It will take a while to cover all drivers. >> > >> > Feel free to apply patches individually. >> >> I looked over the set and they seem good. >> >> Reviewed-by: Alexander Duyck > > Grrr, patch 1 does not apply cleanly to my next-queue tree (dev-queue > branch). I will deal with this series in a day or two, after I have > dealt > with my driver pull requests. Sorry, you will have to replace the ones you took from me. > >> > >> > Changes since v6: >> > clean up between 2..6 and then make your Alex's changes on 1 and 7 >> > The mmiowb shouldn't be needed for Rx. Only one CPU will be running >> > NAPI for the queue and we will synchronize this with a full writel >> > anyway when we re-enable the interrupts. >> > >> > Sinan Kaya (7): >> > i40e/i40evf: Eliminate duplicate barriers on weakly-ordered archs >> > ixgbe: eliminate duplicate barriers on weakly-ordered archs >> > igbvf: eliminate duplicate barriers on weakly-ordered archs >> > igb: eliminate duplicate barriers on weakly-ordered archs >> > fm10k: Eliminate duplicate barriers on weakly-ordered archs >> > ixgbevf: keep writel() closer to wmb() >> > ixgbevf: eliminate duplicate barriers on weakly-ordered archs >> > >> > drivers/net/ethernet/intel/fm10k/fm10k_main.c | 4 ++-- >> > drivers/net/ethernet/intel/i40e/i40e_txrx.c | 14 ++++++++++---- >> > drivers/net/ethernet/intel/i40evf/i40e_txrx.c | 4 ++-- >> > drivers/net/ethernet/intel/igb/igb_main.c | 4 ++-- >> > drivers/net/ethernet/intel/igbvf/netdev.c | 4 ++-- >> > drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 8 ++++---- >> > drivers/net/ethernet/intel/ixgbevf/ixgbevf.h | 5 ----- >> > drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c | 11 ++++++++--- >> > 8 files changed, 30 insertions(+), 24 deletions(-) >> > >> > -- >> > 2.7.4 >> >