Differences

This shows you the differences between two versions of the page.

--- documentation:technical_docs:performance [2019/11/21 17:24] – [Choosing good FreeBSD release] olivier
+++ documentation:technical_docs:performance [2019/12/27 00:18] – [Disabling Hyper Threading (HT)] olivier
@@ Line 27: / Line 27: @@
   * [[http://www.telematica.polito.it/oldsite/courmayeur06/papers/06-A.2.1.pdf|RFC2544 Performance Evaluation for a Linux Based Open Router]] (2006, June)
   * [[http://data.guug.de/slides/lk2008/10G_preso_lk2008.pdf|Towards 10Gb/s open-source routing]] (2008): Include an hardware comparison between a "real" router and a PC.
+  * [[https://wiki.fd.io/images/7/7b/Performance_Consideration_for_packet_processing_on_Intel_Architecture.pptx|Performance consideration for packet processing on Intel Architecture (ppt)]]
 ==== FreeBSD ====
@@ Line 107: / Line 108: @@
 BSDRP is currently following FreeBSD 12-stable branch, to try to have a mix between recent features and stability.
-==== Disabling Hyper Threading ====
+==== Disabling Hyper Threading (HT) ====
-Disable Hyper Threading (HT): By default, lot's of multi-queue NIC drivers create one queue per core.
+By default a multi-queue NIC drivers create one queue per core.
-But "logical" cores didn't help at all for managing interrupts generated by high speed NIC.
+But on older CPU (like Xeon E5-2650 V1) those logical cores didn't help at all for managing interrupts generated by high speed NIC (this is not true on 13-head since [[https://svnweb.freebsd.org/base?view=revision&revision=354338|r354338]] and the new machdep.hyperthreading_intr_allowed that allow interrupts on HTT logical CPUs.
 HT can be disabled with this command:
@@ Line 117: / Line 118: @@
 </code>
-Here is an example on a 8cores x hardware threads Intel CPU and 10G Chelsio NIC:
+Here is an example on a Xeon E5 2650 (8c,16t) and 10G Chelsio NIC where it improve performance by disabling HT:
 <code>
-x HT-enabled-8rxq(default).packets-per-seconds
+x HT-enabled-8rxq(default): inet packets-per-second forwarded
-+ HT-enabled-16rxq.packets-per-seconds
++ HT-enabled-16rxq: inet packets-per-second forwarded
-* HT-disabled.packets-per-seconds
+* HT-disabled-8rxq: inet packets-per-seconds forwarded
 +--------------------------------------------------------------------------+
 |                                                                        **|
@@ Line 144: / Line 145: @@
 </code>
-There is a benefit of about 24% to disable hyper threading.
+There is a benefit of about 24% to disable hyper threading on this old CPU.
+But here is another example where there is a benefit to kept it enabled (and with the NIC configured to uses all the treads) on Xeon E5 2650L (10c, 20t):
+<code>
+x HT on, 8q (default): inet4 packets-per-second forwarded
++ HT off, 8q: inet4 packets-per-second forwarded
+* HT on, 16q: inet4 packets-per-second forwarded
++--------------------------------------------------------------------------+
+|x x              ++                                                   *  *|
+|x xx            +++                                                 * *  *|
+||AM|            |A_|                                                |_MA_||
++--------------------------------------------------------------------------+
+    N           Min           Max        Median           Avg        Stddev
+x   5       4265579     4433699.5     4409249.5     4359580.3       81559.4
++   5       5257621       5443012       5372493     5372693.5     73316.243
+Difference at 95.0% confidence
+.01311e+06 +/- 113098
+.2388% +/- 2.94299%
+        (Student's t, pooled s = 77547.4)
+*   5       8566972       8917315     8734750.5     8769616.1     147186.74
+Difference at 95.0% confidence
+.41004e+06 +/- 173536
+.157% +/- 5.21388%
+        (Student's t, pooled s = 118987)
+</code>
 ==== fastforwarding ====