IOVA allocation improvements for iommu-dma
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Cover letter [PATCH 0/3] IOVA allocation improvements for iommu-dma
Quoted 1 line · Robin Murphy
Hi all,
Hi Robin,
Quoted 14 lines
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!
Quoted 6 lines
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 <[email protected]>
Quoted 13 lines
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 cachesdrivers/iommu/dma-iommu.c | 176 ++++++++++++++++++++++++---------------------- 1 file changed, 90 insertions(+), 86 deletions(-)
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