[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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