[ovs-dev] [PATCH] FAQ: Update performance section regarding CRC32 intrinsics.
Bhanuprakash Bodireddy
bhanuprakash.bodireddy at intel.com
Wed Jul 27 16:15:43 UTC 2016
Signed-off-by: Bhanuprakash Bodireddy <bhanuprakash.bodireddy at intel.com>
---
FAQ.md | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/FAQ.md b/FAQ.md
index 35e1cac..6218feb 100644
--- a/FAQ.md
+++ b/FAQ.md
@@ -688,6 +688,22 @@ A: The OVS kernel datapath may have been updated to a newer version than
recommended to pair the same versions of the kernel module and OVS
userspace.
+### Q: My processor supports special instructions to compute hash and how to leverage them in OVS?
+
+A: OVS should be configured for leveraging the special instructions. For
+ example on X86_64 with SSE4.2 instruction set support, CRC32 intrinsics
+ can be used for efficient hash computation by appending 'msse4.2' to CFLAGS.
+
+ ./configure CFLAGS="-g -O2 -msse4.2"
+
+ If you are on a different processor and don't know what flags to choose, it
+ is recommended to use '-march=native' settings.
+
+ ./configure CFLAGS="-g -O2 -march=native"
+
+ With this, GCC will autodetect the processor and automatically set appropriate
+ flags for it. This should not be used if you are compiling OVS outside the
+ target machine.
Configuration Problems
----------------------
--
2.4.11
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