Re: [PATCH 1/2] iommu: Introduce a rb_tree for looking up device

[Baolu Lu]

On 2023/10/24 16:41, Huang Jiaqing wrote:
> The existing IO page fault handler locates the PCI device by calling
> pci_get_domain_bus_and_slot(), which searches the list of all PCI
> devices until the desired PCI device is found. This is inefficient
> because the algorithm efficiency of searching a list is O(n). In the
> critical path of handling an IO page fault, this is not performance
> friendly given that I/O page fault handling patch is performance
> critical, and parallel heavy dsa_test may cause cpu stuck due to
> the low efficiency and lock competition in current path.
>
> To improve the performance of the IO page fault handler, replace
> pci_get_domain_bus_and_slot() with a local red-black tree. A red-black
> tree is a self-balancing binary search tree, which means that the
> average time complexity of searching a red-black tree is O(log(n)). This
> is significantly faster than O(n), so it can significantly improve the
> performance of the IO page fault handler.
>
> In addition, we can only insert the affected devices (those that have IO
> page fault enabled) into the red-black tree. This can further improve
> the performance of the IO page fault handler.
>
> This series depends on "deliver page faults to user space" patch-set:
> https://lore.kernel.org/linux-iommu/20230928042734.16134-1-baolu.lu@xxxxxxxxxxxxxxx/

The note above is not part of the commit message, and should be placed
below the tear line or in the cover letter, if there is one.

> Signed-off-by: Huang Jiaqing <jiaqing.huang@xxxxxxxxx>
> ---
>   drivers/iommu/io-pgfault.c | 104 ++++++++++++++++++++++++++++++++++++-
>   include/linux/iommu.h      |  16 ++++++
>   2 files changed, 118 insertions(+), 2 deletions(-)

Best regards,
baolu