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[ovs-dev] FAQ: Update performance section regarding CRC32 intrinsics.

Message ID 1469636143-27682-1-git-send-email-bhanuprakash.bodireddy@intel.com
State Superseded
Headers show

Commit Message

Bodireddy, Bhanuprakash July 27, 2016, 4:15 p.m. UTC 
Signed-off-by: Bhanuprakash Bodireddy <bhanuprakash.bodireddy@intel.com>
---
 FAQ.md | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

Comments

Ben Pfaff July 27, 2016, 4:27 p.m. UTC | #1 
On Wed, Jul 27, 2016 at 05:15:43PM +0100, Bhanuprakash Bodireddy wrote:
> Signed-off-by: Bhanuprakash Bodireddy <bhanuprakash.bodireddy@intel.com>

This probably makes better sense in INSTALL.md.
diff mbox

Patch

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
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