On Wed, Jul 24, 2019 at 10:58:26AM +0100, John Garry wrote: > On 11/07/2019 18:19, Will Deacon wrote: > > This is a significant rework of the RFC I previously posted here: > > > > https://lkml.kernel.org/r/[email protected] > > > > But this time, it looks like it might actually be worthwhile according > > to my perf profiles, where __iommu_unmap() falls a long way down the > > profile for a multi-threaded netperf run. I'm still relying on others to > > confirm this is useful, however. > > > > Some of the changes since last time are: > > > > * Support for constructing and submitting a list of commands in the > > driver > > > > * Numerous changes to the IOMMU and io-pgtable APIs so that we can > > submit commands in batches > > > > * Removal of cmpxchg() from cmdq_shared_lock() fast-path > > > > * Code restructuring and cleanups > > > > This current applies against my iommu/devel branch that Joerg has pulled > > for 5.3. If you want to test it out, I've put everything here: > > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git/log/?h=iommu/cmdq > > > > Feedback welcome. I appreciate that we're in the merge window, but I > > wanted to get this on the list for people to look at as an RFC. > > > > I tested storage performance on this series, which I think is a better > scenario to test than network performance, that being generally limited by > the network link speed.
Interesting, thanks for sharing. Do you also see a similar drop in CPU time to the one reported by Ganapat? > Baseline performance (will/iommu/devel, commit 9e6ea59f3) > 8x SAS disks D05 839K IOPS > 1x NVMe D05 454K IOPS > 1x NVMe D06 442k IOPS > > Patchset performance (will/iommu/cmdq) > 8x SAS disk D05 835K IOPS > 1x NVMe D05 472K IOPS > 1x NVMe D06 459k IOPS > > So we see a bit of an NVMe boost, but about the same for 8x disks. No iommu > performance is about 918K IOPs for 8x disks, so it is not limited by the > medium. It would be nice to know if this performance gap is because of Linux, or simply because of the translation overhead in the SMMU hardware. Are you able to get a perf profile to see where we're spending time? Thanks, Will _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
