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[POWERPC] Use 4kB iommu pages even on 64kB-page systems

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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 <linas@austin.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>
This commit is contained in:
Linas Vepstas
2006-10-30 16:15:59 +11:00
committed by Paul Mackerras
parent dd6c89f686
commit 5d2efba64b
8 changed files with 80 additions and 81 deletions
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1
arch/powerpc/sysdev/dart.h
View File

@@ -72,7 +72,6 @@
#define DART_PAGE_SHIFT 12
#define DART_PAGE_SIZE (1 << DART_PAGE_SHIFT)
#define DART_PAGE_FACTOR (PAGE_SHIFT - DART_PAGE_SHIFT)
#endif /* _POWERPC_SYSDEV_DART_H */

8
arch/powerpc/sysdev/dart_iommu.c
View File

@@ -156,9 +156,6 @@ static void dart_build(struct iommu_table *tbl, long index,
DBG("dart: build at: %lx, %lx, addr: %x\n", index, npages, uaddr);
index <<= DART_PAGE_FACTOR;
npages <<= DART_PAGE_FACTOR;
dp = ((unsigned int*)tbl->it_base) + index;
/* On U3, all memory is contigous, so we can move this
@@ -199,9 +196,6 @@ static void dart_free(struct iommu_table *tbl, long index, long npages)
DBG("dart: free at: %lx, %lx\n", index, npages);
index <<= DART_PAGE_FACTOR;
npages <<= DART_PAGE_FACTOR;
dp = ((unsigned int *)tbl->it_base) + index;
while (npages--)
@@ -281,7 +275,7 @@ static void iommu_table_dart_setup(void)
iommu_table_dart.it_busno = 0;
iommu_table_dart.it_offset = 0;
/* it_size is in number of entries */
iommu_table_dart.it_size = (dart_tablesize / sizeof(u32)) >> DART_PAGE_FACTOR;
iommu_table_dart.it_size = dart_tablesize / sizeof(u32);
/* Initialize the common IOMMU code */
iommu_table_dart.it_base = (unsigned long)dart_vbase;