From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joerg Roedel Subject: Re: [PATCH] iommu/amd - Optimize PPR log handling Date: Wed, 30 May 2018 06:52:04 +0200 Message-ID: <20180530045203.GO18595@8bytes.org> References: <152668031618.108078.8188026193559324640.stgit@wsp141332wss.amd.com> <20180529145405.GN18595@8bytes.org> <223930b9-3df9-813a-6676-68072e4e1bb6@amd.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <223930b9-3df9-813a-6676-68072e4e1bb6-5C7GfCeVMHo@public.gmane.org> 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: Gary R Hook Cc: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: iommu@lists.linux-foundation.org On Tue, May 29, 2018 at 12:28:54PM -0500, Gary R Hook wrote: > No, no numbers. We're still working out how best to test this, and > suggestions/strategies are welcome. Maybe run a simple kernel on the CPU that does a memcpy on a larger portion of mmapped (but yet unmapped) process address space and measure the time it takes for the kernel to run. The page-fault path in the iommu-driver is only a small part of the involved code here, but maybe you already see a difference. Doing a u-benchmark only for that code is probably a bit more challenging. > The change is modeled after the function iommu_poll_events(), which is much > cleaner. The GA log handling should be changed, as well (there are > superfluous writes in the loop), but I figured, "one thing at a time". This > is admittedly a minor optimization, but discussions with Tom Lendacky have > led us down this path. > > Your feedback is appreciated. Yeah, the patch looks good to me from my first review. But since I can't test that code myself I was wondering if you did any tests and can share something with me to run my own tests :) Joerg