Re: [PATCH -mm 0/3] convert IOMMUs to use iova
- From: FUJITA Tomonori <tomof@xxxxxxx>
- Date: Sat, 3 Nov 2007 03:11:29 +0900
On Fri, 2 Nov 2007 19:12:27 +0200
Muli Ben-Yehuda <muli@xxxxxxxxxx> wrote:
On Sat, Nov 03, 2007 at 02:05:39AM +0900, FUJITA Tomonori wrote:
This patchset convert the PPC64 IOMMU to use the iova code for free
area management.
The IOMMUs ignores low level drivers' restrictions, the maximum
segment size and segment boundary.
I fixed the former:
http://thread.gmane.org/gmane.linux.scsi/35602
The latter makes the free area management complicated. I'd like to
convert IOMMUs to use the iova code (that intel-iommu introduced)
for free area management and enable iova to handle segment boundary
restrictions, rather than fixing all the IOMMUs' free area
management,
In general it sounds like a great idea, but have you looked at what
impact this has on the performance of the IO path?
Not yet. And I have access to only an entry-class pSeries server so I
would appreciate it if POWERPC people try the patchset with high-end
servers.
The patchset doesn't use the tricks that the current POWERPC IOMMU use
to improve performance (Anton and Olof told me about them, Thanks!)
. So I might need to modify iova for them.
I think that it's difficult to use some tricks used in the IOMMUs with
the iova even if we modify the iova. If the iova degrades performance,
I think that it would be better to have new IOMMU library code to use
simply a bit map that most of the IOMMUs use.
Another possible factor to degrade performance is that we can't
allocate areas for map_sg at one stroke like some of the IOMMUs do.
We need to allocate an area per sg segment to handle segment boundary.
If it's unacceptable, I guess that there is only one way, LLDs
allocate many sg entries and then the IOMMU splits the sg entryes.
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- From: FUJITA Tomonori
- Re: [PATCH -mm 0/3] convert IOMMUs to use iova
- From: Muli Ben-Yehuda
- [PATCH -mm 0/3] convert IOMMUs to use iova
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