docs: dpdk extended the initial note

[collectd.git] / docs / BUILD.dpdkstat.md

diff --git a/docs/BUILD.dpdkstat.md b/docs/BUILD.dpdkstat.md
index b502edd..b60c182 100644 (file)
--- a/docs/BUILD.dpdkstat.md
+++ b/docs/BUILD.dpdkstat.md
@@ -1,7 +1,17 @@
 # The dpdkstat plugin
 
+This plugin is optional and only has a specific use case: monitoring DPDK applications
+that don't expose stats in any other way than the DPDK xstats API.
+
 **Data Plane Development Kit** (DPDK) is a set of drivers and libraries for fast
-packet processing.
+packet processing. Please note that this plugin is a polling based plugin rather
+than an events based plugin (using it will drive up core utilization on a system).
+
+**PLEASE DO NOT USE THIS PLUGIN FOR OVS-DPDK**. dpdkstat is really for DPDK
+applications that have no other way of exposing stats. For OVS or OVS-with-DPDK the
+Open vSwitch plugins available in collectd Version 5.8.0 should be used for
+collecting stats and events. In addition the OVS plugin is events based rather
+than polling based and will have a smaller footprint on the system.
 
 ## Summary
 
@@ -51,8 +61,8 @@ instruction set manually:
         mount -t hugetlbfs nodev /mnt/huge
         echo 64 > /sys/devices/system/node/node0/hugepages/hugepages-2048kB/nr_hugepages
 
- *  To configure the DPDK build for the combined shared library modify
-    `config/common_base` in your DPDK as follows
+ *  To configure the DPDK build for the combined shared library and enable autoload
+    of pmd drivers modify `config/common_base` in your DPDK as follows
 
         #
         # Compile to share library
@@ -60,6 +70,10 @@ instruction set manually:
         -CONFIG_RTE_BUILD_SHARED_LIB=n
         +CONFIG_RTE_BUILD_SHARED_LIB=y
 
+        # Default driver path (or "" to disable)
+        -CONFIG_RTE_EAL_PMD_PATH=""
+        +CONFIG_RTE_EAL_PMD_PATH="/usr/lib/dpdk-pmd/"
+
  *  Prepare the configuration for the appropriate target as specified at:
     http://dpdk.org/doc/guides/linux_gsg/build_dpdk.html.
 
@@ -75,6 +89,14 @@ instruction set manually:
 
         sudo make install prefix=/usr
 
+ *  Create dpdk-pmd folder
+
+        mkdir -p /usr/lib/dpdk-pmd
+
+ *  Create symlinks to pmd drivers
+
+        find /usr/lib -type f -name 'librte_pmd*' | while read path ; do ln -s $path /usr/lib/dpdk-pmd/`echo $path | grep -o 'librte_.*so'` ;  done
+
     **Note 1:** You must run make install as the configuration of collectd with
     DPDK expects DPDK to be installed somewhere.
 
@@ -84,6 +106,9 @@ instruction set manually:
     **Note 3:** If you are not root then use sudo to make install DPDK to the
     appropriate location.
 
+    **Note 4:** You **MUST** create symlink to a NIC driver lib. This way collectd
+    will be able to work with device bound to dpdk.
+
  *  Check that the DPDK library has been installed in `/usr/lib` or `/lib`:
 
         ls /usr/lib | grep dpdk