dpdk: Limit DPDK memory usage.

Since 18.05 release, DPDK moved to dynamic memory model in which
hugepages could be allocated on demand. At the same time '--socket-mem'
option was re-defined as a size of pre-allocated memory, i.e. memory
that should be allocated at startup and could not be freed.
So, DPDK with a new memory model could allocate more hugepage memory
than specified in '--socket-mem' or '-m' options.

This change adds new configurable 'other_config:dpdk-socket-limit'
which could be used to limit the ammount of memory DPDK could use.
It uses new DPDK option '--socket-limit'.
Ex.:

  ovs-vsctl set Open_vSwitch . other_config:dpdk-socket-limit="1024,1024"

Also, in order to preserve old behaviour, if '--socket-limit' is not
specified, it will be defaulted to the amount of memory specified by
'--socket-mem' option, i.e. OVS will not be able to allocate more.
This is needed, for example, to disallow OVS to allocate more memory
than reserved for it by Nova in OpenStack installations.

Signed-off-by: Ilya Maximets <i.maximets@samsung.com>
Signed-off-by: Ian Stokes <ian.stokes@intel.com>

NEWS

@@ -1,5 +1,8 @@
 Post-v2.11.0
 ---------------------
+   - DPDK:
+     * New option 'other_config:dpdk-socket-limit' to limit amount of
+       hugepage memory that can be used by DPDK.
 
 
 v2.11.0 - xx xxx xxxx

lib/dpdk.c

@@ -100,8 +100,9 @@ construct_dpdk_options(const struct smap *ovs_other_config, struct svec *args)
         bool default_enabled;
         const char *default_value;
     } opts[] = {
-        {"dpdk-lcore-mask", "-c", false, NULL},
+        {"dpdk-lcore-mask",   "-c",             false, NULL},
-        {"dpdk-hugepage-dir", "--huge-dir", false, NULL},
+        {"dpdk-hugepage-dir", "--huge-dir",     false, NULL},
+        {"dpdk-socket-limit", "--socket-limit", false, NULL},
     };
 
     int i;
@@ -318,6 +319,22 @@ dpdk_init__(const struct smap *ovs_other_config)
     svec_add(&args, ovs_get_program_name());
     construct_dpdk_args(ovs_other_config, &args);
 
+    if (!args_contains(&args, "--legacy-mem")
+        && !args_contains(&args, "--socket-limit")) {
+        const char *arg;
+        size_t i;
+
+        SVEC_FOR_EACH (i, arg, &args) {
+            if (!strcmp(arg, "--socket-mem")) {
+                break;
+            }
+        }
+        if (i < args.n - 1) {
+            svec_add(&args, "--socket-limit");
+            svec_add(&args, args.names[i + 1]);
+        }
+    }
+
     if (args_contains(&args, "-c") || args_contains(&args, "-l")) {
         auto_determine = false;
     }

vswitchd/vswitch.xml

@@ -333,6 +333,28 @@
         </p>
       </column>
 
+      <column name="other_config" key="dpdk-socket-limit"
+              type='{"type": "string"}'>
+        <p>
+          Limits the maximum amount of memory that can be used from the
+          hugepage pool, on a per-socket basis.
+        </p>
+        <p>
+          The specifier is a comma-separated list of memory limits per socket.
+          <code>0</code> will disable the limit for a particular socket.
+        </p>
+        <p>
+          If not specified, OVS will configure limits equal to the amount of
+          preallocated memory specified by <ref column="other_config"
+          key="dpdk-socket-mem"/> or <code>--socket-mem</code> in
+          <ref column="other_config" key="dpdk-extra"/>. If none of the above
+          options specified or <code>--legacy-mem</code> provided in
+          <ref column="other_config" key="dpdk-extra"/>, limits will not be
+          applied.
+          Changing this value requires restarting the daemon.
+        </p>
+      </column>
+
       <column name="other_config" key="dpdk-hugepage-dir"
               type='{"type": "string"}'>
         <p>