On Mon, Mar 19, 2018 at 10:47:42PM -0400, 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. > > Changes since v3: > - https://www.spinics.net/lists/arm-kernel/msg641851.html > - group patches together into subsystems ib:... > - collect reviewed and tested bys > - scrub barrier() > Sinan Kaya (6): > IB/mlx4: Eliminate duplicate barriers on weakly-ordered archs > infiniband: cxgb4: Eliminate duplicate barriers on weakly-ordered > archs I took these two patches to for-next since they seem OK to me > RDMA/bnxt_re: Eliminate duplicate barriers on weakly-ordered archs > RDMA/i40iw: Eliminate duplicate barriers on weakly-ordered archs > IB/nes: Eliminate duplicate barriers on weakly-ordered archs > RDMA/qedr: eliminate duplicate barriers on weakly-ordered archs #2 These will need their comments addressed Thanks, Jason -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
