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| author | Borislav Petkov <borislav.petkov@amd.com> | 2011-08-05 15:15:08 +0200 |
|---|---|---|
| committer | H. Peter Anvin <hpa@linux.intel.com> | 2011-08-05 21:26:44 +0200 |
| commit | dfb09f9b7ab03fd367740e541a5caf830ed56726 (patch) | |
| tree | 8bd8fdbbf3fb67f7d0aed73a1e8e1c7034ed2d54 /Documentation/kernel-parameters.txt | |
| parent | Merge commit 'v3.0' into x86/cpu (diff) | |
| download | linux-dfb09f9b7ab03fd367740e541a5caf830ed56726.tar.xz linux-dfb09f9b7ab03fd367740e541a5caf830ed56726.zip | |
x86, amd: Avoid cache aliasing penalties on AMD family 15h
This patch provides performance tuning for the "Bulldozer" CPU. With its
shared instruction cache there is a chance of generating an excessive
number of cache cross-invalidates when running specific workloads on the
cores of a compute module.
This excessive amount of cross-invalidations can be observed if cache
lines backed by shared physical memory alias in bits [14:12] of their
virtual addresses, as those bits are used for the index generation.
This patch addresses the issue by clearing all the bits in the [14:12]
slice of the file mapping's virtual address at generation time, thus
forcing those bits the same for all mappings of a single shared library
across processes and, in doing so, avoids instruction cache aliases.
It also adds the command line option "align_va_addr=(32|64|on|off)" with
which virtual address alignment can be enabled for 32-bit or 64-bit x86
individually, or both, or be completely disabled.
This change leaves virtual region address allocation on other families
and/or vendors unaffected.
Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
Link: http://lkml.kernel.org/r/1312550110-24160-2-git-send-email-bp@amd64.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Diffstat (limited to 'Documentation/kernel-parameters.txt')
| -rw-r--r-- | Documentation/kernel-parameters.txt | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index aa47be71df4c..af73c036b7e6 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -299,6 +299,19 @@ bytes respectively. Such letter suffixes can also be entirely omitted. behaviour to be specified. Bit 0 enables warnings, bit 1 enables fixups, and bit 2 sends a segfault. + align_va_addr= [X86-64] + Align virtual addresses by clearing slice [14:12] when + allocating a VMA at process creation time. This option + gives you up to 3% performance improvement on AMD F15h + machines (where it is enabled by default) for a + CPU-intensive style benchmark, and it can vary highly in + a microbenchmark depending on workload and compiler. + + 1: only for 32-bit processes + 2: only for 64-bit processes + on: enable for both 32- and 64-bit processes + off: disable for both 32- and 64-bit processes + amd_iommu= [HW,X86-84] Pass parameters to the AMD IOMMU driver in the system. Possible values are: |