From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nate Watterson Subject: Re: [PATCH 0/3] IOVA allocation improvements for iommu-dma Date: Wed, 22 Mar 2017 13:43:16 -0400 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Robin Murphy Cc: will.deacon-5wv7dgnIgG8@public.gmane.org, damm+renesas-yzvPICuk2ACczHhG9Qg4qA@public.gmane.org, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, sunil.kovvuri-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org List-Id: iommu@lists.linux-foundation.org On 2017-03-15 09:33, Robin Murphy wrote: > Hi all, Hi Robin, > > Here's the first bit of lock contention removal to chew on - feedback > welcome! Note that for the current users of the io-pgtable framework, > this is most likely to simply push more contention onto the io-pgtable > lock, so may not show a great improvement alone. Will and I both have > rough proof-of-concept implementations of lock-free io-pgtable code > which we need to sit down and agree on at some point, hopefullt fairly > soon. > > I've taken the opportunity to do a bit of cleanup and refactoring > within the series to make the final state of the code nicer, but the > diffstat still turns out surprisingly reasonable in the end - it would > actually be negative but for the new comments! > > Magnus, Shimoda-san, the first two patches should be of interest as > they > constitute the allocation rework I mentioned a while back[1] - if you > still need to implement that scary workaround, this should make it > simple to hook IPMMU-specific calls into the alloc and free paths, and > let the driver take care of the details internally. I've tested your patches on a QDF2400 platform and generally see modest improvements in iperf/fio performance. As you suspected would happen, contention has indeed moved to the io-pgtable lock. I am looking forward to testing with the lock-free io-pgtable implementation, however I suspect that there will still be contention issues acquiring the (SMMUv3) cmdq lock on the unmap path. Reviewed/Tested-by: Nate Watterson > > Robin. > > [1]:https://lists.linuxfoundation.org/pipermail/iommu/2017-January/020189.html > > Robin Murphy (3): > iommu/dma: Convert to address-based allocation > iommu/dma: Clean up MSI IOVA allocation > iommu/dma: Plumb in the per-CPU IOVA caches > > drivers/iommu/dma-iommu.c | 176 > ++++++++++++++++++++++++---------------------- > 1 file changed, 90 insertions(+), 86 deletions(-) -- Qualcomm Datacenter Technologies, Inc. on behalf of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.