lkml.org 
[lkml]   [2021]   [Mar]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 0/6] dma mapping/iommu: Allow IOMMU IOVA rcache range to be configured
On Fri, Mar 19, 2021 at 09:25:42PM +0800, John Garry wrote:
> For streaming DMA mappings involving an IOMMU and whose IOVA len regularly
> exceeds the IOVA rcache upper limit (meaning that they are not cached),
> performance can be reduced.
>
> This is much more pronounced from commit 4e89dce72521 ("iommu/iova: Retry
> from last rb tree node if iova search fails"), as discussed at [0].
>
> IOVAs which cannot be cached are highly involved in the IOVA aging issue,
> as discussed at [1].

I'm confused. If this a limit in the IOVA allocator, dma-iommu should
be able to just not grow the allocation so larger without help from
the driver.

If contrary to the above description it is device-specific, the driver
could simply use dma_get_max_seg_size().

\
 
 \ /
  Last update: 2021-03-19 14:41    [W:0.090 / U:0.012 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site