Hi all,
Can anyone help review it?
On 2019/8/15 20:11, Zhen Lei wrote:
> v1 --> v2
> 1. I did not chagne the patches but added this cover-letter.
> 2. Add a batch of reviewers base on
> 9257b4a206fc ("iommu/iova: introduce per-cpu caching to iova allocation")
> 3. I described the problem I met in patch 2, but I hope below brief
> description
> can help people to quickly understand.
> Suppose there are six rcache sizes, each size can maximum hold 10000 IOVAs.
> --------------------------------------------
> | 4K | 8K | 16K | 32K | 64K | 128K |
> --------------------------------------------
> | 10000 | 9000 | 8500 | 8600 | 9200 | 7000 |
> --------------------------------------------
> As the above map displayed, the whole rcache buffered too many IOVAs. Now,
> the
> worst case can be coming, suppose we need 20000 4K IOVAs at one time. That
> means
> 10000 IOVAs can be allocated from rcache, but another 10000 IOVAs should
> be
> allocated from RB tree base on alloc_iova() function. But the RB tree
> currently
> have at least (9000 + 8500 + 8600 + 9200 + 7000) = 42300 nodes. The
> average speed
> of RB tree traverse will be very slow. For my test scenario, the 4K size
> IOVAs are
> frequently used, but others are not. So similarly, when the 20000 4K IOVAs
> are
> continuous freed, the first 10000 IOVAs can be quickly buffered, but the
> other
> 10000 IOVAs can not.
>
> Zhen Lei (2):
> iommu/iova: introduce iova_magazine_compact_pfns()
> iommu/iova: enhance the rcache optimization
>
> drivers/iommu/iova.c | 100
> +++++++++++++++++++++++++++++++++++++++++++++++----
> include/linux/iova.h | 1 +
> 2 files changed, 95 insertions(+), 6 deletions(-)
>
