Re: [PATCH 0/4] iommu: remove lock contention in iova allocation

[Shaohua Li <shli-b10kYP2dOMg@public.gmane.org>]

Ping!

On Tue, Nov 24, 2015 at 01:54:06PM -0800, Shaohua Li wrote:
> Hi,
> 
> The lock contention in iova allocation is very significant. In my iperf test
> with intel 10Gbps NIC card with 48 threads, I observed 99% cpu time is spending
> on the lock contention. In the test:
> 
> CPU utilization 100%, iperf reports ~1Gbps
> 
> The patches introduce a bitmap based approach for dma address allocation. It
> completetly avoids the lock contention. Run the same test:
> 
> CPU utilization 1%, iperf reports 9.3Gbps
> 
> I also tried the test with the patch, but disable bitmap. The result is the
> same as that without the patch.
> 
> The patches only work for DMA less than 8k, which is the most comman case we
> have highest request(DMA) per second. Bigger size DMA still fallback to rbtree
> based allocation. But if required and DAC is enabled by default, it's easy to
> support bigger size DMA in the bitmap allocation.
> 
> Thanks,
> Shaohua
> 
> 
> Shaohua Li (4):
>   iommu: alloc_iova returns a pfn
>   iommu: add a bitmap based dma address allocator
>   iommu: enable bitmap allocation for intel iommu
>   iommu: free_iova doesn't need lock twice
> 
>  drivers/iommu/dma-iommu.c   |  32 ++++-----
>  drivers/iommu/intel-iommu.c |  96 ++++++++++++++++-----------
>  drivers/iommu/iova.c        | 157 +++++++++++++++++++++++++++++++++-----------
>  include/linux/iova.h        |  21 ++++--
>  4 files changed, 210 insertions(+), 96 deletions(-)
> 
> -- 
> 2.4.6
>