diff options
| author | David Mosberger <davidm@tiger.hpl.hp.com> | 2003-07-25 04:44:18 -0700 |
|---|---|---|
| committer | David Mosberger <davidm@tiger.hpl.hp.com> | 2003-07-25 04:44:18 -0700 |
| commit | c8daa92df131dcffabcc29cffd1a10fe56e6860b (patch) | |
| tree | 003887ce3b1642206013096969b93a56a20b0e3e | |
| parent | 3a883dd4a646df9f6b35bd77338d3bb3cce2734d (diff) | |
ia64: Turn BIO-level virtual merging off again, so we can turn I/O MMU
bypassing on again, which is more beneficial, performance-wise.
| -rw-r--r-- | arch/ia64/hp/common/sba_iommu.c | 6 | ||||
| -rw-r--r-- | include/asm-ia64/io.h | 11 |
2 files changed, 15 insertions, 2 deletions
diff --git a/arch/ia64/hp/common/sba_iommu.c b/arch/ia64/hp/common/sba_iommu.c index 85db8f8eb1bd..fc9b8deaac55 100644 --- a/arch/ia64/hp/common/sba_iommu.c +++ b/arch/ia64/hp/common/sba_iommu.c @@ -48,9 +48,11 @@ ** This option allows cards capable of 64bit DMA to bypass the IOMMU. If ** not defined, all DMA will be 32bit and go through the TLB. ** There's potentially a conflict in the bio merge code with us -** advertising an iommu, but then bypassing it. Disabled for now. +** advertising an iommu, but then bypassing it. Since I/O MMU bypassing +** appears to give more performance than bio-level virtual merging, we'll +** do the former for now. */ -#undef ALLOW_IOV_BYPASS +#define ALLOW_IOV_BYPASS /* ** If a device prefetches beyond the end of a valid pdir entry, it will cause diff --git a/include/asm-ia64/io.h b/include/asm-ia64/io.h index cc2f3d6803c3..2ff2d00ef3ed 100644 --- a/include/asm-ia64/io.h +++ b/include/asm-ia64/io.h @@ -414,6 +414,16 @@ extern void __ia64_memset_c_io (unsigned long, unsigned long, long); # endif /* __KERNEL__ */ /* + * Enabling BIO_VMERGE_BOUNDARY forces us to turn off I/O MMU bypassing. It is said that + * BIO-level virtual merging can give up to 4% performance boost (not verified for ia64). + * On the other hand, we know that I/O MMU bypassing gives ~8% performance improvement on + * SPECweb-like workloads on zx1-based machines. Thus, for now we favor I/O MMU bypassing + * over BIO-level virtual merging. + */ +#if 1 +#define BIO_VMERGE_BOUNDARY 0 +#else +/* * It makes no sense at all to have this BIO_VMERGE_BOUNDARY macro here. Should be * replaced by dma_merge_mask() or something of that sort. Note: the only way * BIO_VMERGE_BOUNDARY is used is to mask off bits. Effectively, our definition gets @@ -425,5 +435,6 @@ extern void __ia64_memset_c_io (unsigned long, unsigned long, long); */ extern unsigned long ia64_max_iommu_merge_mask; #define BIO_VMERGE_BOUNDARY (ia64_max_iommu_merge_mask + 1) +#endif #endif /* _ASM_IA64_IO_H */ |