From 5d2efba64b231a1733c4048d1708d77e07f26426 Mon Sep 17 00:00:00 2001 From: Linas Vepstas Date: Mon, 30 Oct 2006 16:15:59 +1100 Subject: [POWERPC] Use 4kB iommu pages even on 64kB-page systems The 10Gigabit ethernet device drivers appear to be able to chew up all 256MB of TCE mappings on pSeries systems, as evidenced by numerous error messages: iommu_alloc failed, tbl c0000000010d5c48 vaddr c0000000d875eff0 npages 1 Some experimentation indicates that this is essentially because one 1500 byte ethernet MTU gets mapped as a 64K DMA region when the large 64K pages are enabled. Thus, it doesn't take much to exhaust all of the available DMA mappings for a high-speed card. This patch changes the iommu allocator to work with its own unique, distinct page size. Although the patch is long, its actually quite simple: it just #defines a distinct IOMMU_PAGE_SIZE and then uses this in all the places that matter. As a side effect, it also dramatically improves network performance on platforms with H-calls on iommu translation inserts/removes (since we no longer call it 16 times for a 1500 bytes packet when the iommu HW is still 4k). In the future, we might want to make the IOMMU_PAGE_SIZE a variable in the iommu_table instance, thus allowing support for different HW page sizes in the iommu itself. Signed-off-by: Linas Vepstas Signed-off-by: Benjamin Herrenschmidt Acked-by: Olof Johansson Acked-by: Stephen Rothwell Signed-off-by: Paul Mackerras --- arch/powerpc/kernel/vio.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'arch/powerpc/kernel/vio.c') diff --git a/arch/powerpc/kernel/vio.c b/arch/powerpc/kernel/vio.c index cb87e71eec6..ed007878d1b 100644 --- a/arch/powerpc/kernel/vio.c +++ b/arch/powerpc/kernel/vio.c @@ -92,9 +92,9 @@ static struct iommu_table *vio_build_iommu_table(struct vio_dev *dev) &tbl->it_index, &offset, &size); /* TCE table size - measured in tce entries */ - tbl->it_size = size >> PAGE_SHIFT; + tbl->it_size = size >> IOMMU_PAGE_SHIFT; /* offset for VIO should always be 0 */ - tbl->it_offset = offset >> PAGE_SHIFT; + tbl->it_offset = offset >> IOMMU_PAGE_SHIFT; tbl->it_busno = 0; tbl->it_type = TCE_VB; -- cgit v1.2.3