Messages in this thread |  | | From | Chao Gao <> | Subject | [RFC v2 0/2] swiotlb performance optimizations | Date | Mon, 18 Jul 2022 09:28:16 +0800 |
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Intent of this post: Seek reviews from Intel reviewers and anyone else in the list interested in IO performance in confidential VMs. Need some acked-by reviewed-by tags before I can add swiotlb maintainers to "to/cc" lists and ask for a review from them.
Changes from v1 to v2: - rebase to the latest dma-mapping tree. - drop the duplicate patch for mitigating lock contention - re-collect perf data
swiotlb is now widely used by confidential VMs. This series optimizes swiotlb to reduce cache misses and lock contention during bounce buffer allocation/free and memory bouncing to improve IO workload performance in confidential VMs.
Here are some FIO tests we did to demonstrate the improvement.
Test setup ----------
A normal VM with 8vCPU and 32G memory, swiotlb is enabled by swiotlb=force. FIO block size is 4K and iodepth is 256. Note that a normal VM is used so that others lack of necessary hardware to host confidential VMs can reproduce results below.
Results -------
1 FIO job read/write IOPS (k) vanilla read 216 write 251 optimized read 250 write 270
1-job FIO sequential read/write perf increase by 19% and 8% respectively.
Chao Gao (2): swiotlb: use bitmap to track free slots swiotlb: Allocate memory in a cache-friendly way
include/linux/swiotlb.h | 8 ++- kernel/dma/swiotlb.c | 127 +++++++++++++++++----------------------- 2 files changed, 60 insertions(+), 75 deletions(-)
-- 2.25.1
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