[ovs-dev] [v13 05/12] dpif-netdev: Add command to switch dpif implementation.

Cian Ferriter cian.ferriter at intel.com
Thu Jun 17 16:18:18 UTC 2021


From: Harry van Haaren <harry.van.haaren at intel.com>

This commit adds a new command to allow the user to switch
the active DPIF implementation at runtime. A probe function
is executed before switching the DPIF implementation, to ensure
the CPU is capable of running the ISA required. For example, the
below code will switch to the AVX512 enabled DPIF assuming
that the runtime CPU is capable of running AVX512 instructions:

 $ ovs-appctl dpif-netdev/dpif-set dpif_avx512

A new configuration flag is added to allow selection of the
default DPIF. This is useful for running the unit-tests against
the available DPIF implementations, without modifying each unit test.

The design of the testing & validation for ISA optimized DPIF
implementations is based around the work already upstream for DPCLS.
Note however that a DPCLS lookup has no state or side-effects, allowing
the auto-validator implementation to perform multiple lookups and
provide consistent statistic counters.

The DPIF component does have state, so running two implementations in
parallel and comparing output is not a valid testing method, as there
are changes in DPIF statistic counters (side effects). As a result, the
DPIF is tested directly against the unit-tests.

Signed-off-by: Harry van Haaren <harry.van.haaren at intel.com>
Co-authored-by: Cian Ferriter <cian.ferriter at intel.com>
Signed-off-by: Cian Ferriter <cian.ferriter at intel.com>

---

v13:
- Add Docs items about the switch DPIF command here rather than in
  later commit.
- Document operation in manpages as well as rST.
- Minor code refactoring to address review comments.
---
 Documentation/topics/dpdk/bridge.rst |  34 +++++++++
 acinclude.m4                         |  15 ++++
 configure.ac                         |   1 +
 lib/automake.mk                      |   1 +
 lib/dpif-netdev-avx512.c             |  14 ++++
 lib/dpif-netdev-private-dpif.c       | 103 +++++++++++++++++++++++++++
 lib/dpif-netdev-private-dpif.h       |  49 ++++++++++++-
 lib/dpif-netdev-private-thread.h     |  11 +--
 lib/dpif-netdev-unixctl.man          |   3 +
 lib/dpif-netdev.c                    |  89 +++++++++++++++++++++--
 10 files changed, 304 insertions(+), 16 deletions(-)
 create mode 100644 lib/dpif-netdev-private-dpif.c

diff --git a/Documentation/topics/dpdk/bridge.rst b/Documentation/topics/dpdk/bridge.rst
index 526d5c959..fafa8c821 100644
--- a/Documentation/topics/dpdk/bridge.rst
+++ b/Documentation/topics/dpdk/bridge.rst
@@ -214,3 +214,37 @@ implementation ::
 
 Compile OVS in debug mode to have `ovs_assert` statements error out if
 there is a mis-match in the DPCLS lookup implementation.
+
+Datapath Interface Performance
+------------------------------
+
+The datapath interface (DPIF) or dp_netdev_input() is responsible for taking
+packets through the major components of the userspace datapath; such as
+miniflow_extract, EMC, SMC and DPCLS lookups, and a lot of the performance
+stats associated with the datapath.
+
+Just like with the SIMD DPCLS feature above, SIMD can be applied to the DPIF to
+improve performance.
+
+By default, dpif_scalar is used. The DPIF implementation can be selected by
+name ::
+
+    $ ovs-appctl dpif-netdev/dpif-set dpif_avx512
+    DPIF implementation set to dpif_avx512.
+
+    $ ovs-appctl dpif-netdev/dpif-set dpif_scalar
+    DPIF implementation set to dpif_scalar.
+
+Running Unit Tests with AVX512 DPIF
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Since the AVX512 DPIF is disabled by default, a compile time option is
+available in order to test it with the OVS unit test suite. When building with
+a CPU that supports AVX512, use the following configure option ::
+
+    $ ./configure --enable-dpif-default-avx512
+
+The following line should be seen in the configure output when the above option
+is used ::
+
+    checking whether DPIF AVX512 is default implementation... yes
diff --git a/acinclude.m4 b/acinclude.m4
index 15a54d636..5fbcd9872 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -30,6 +30,21 @@ AC_DEFUN([OVS_CHECK_DPCLS_AUTOVALIDATOR], [
   fi
 ])
 
+dnl Set OVS DPIF default implementation at configure time for running the unit
+dnl tests on the whole codebase without modifying tests per DPIF impl
+AC_DEFUN([OVS_CHECK_DPIF_AVX512_DEFAULT], [
+  AC_ARG_ENABLE([dpif-default-avx512],
+                [AC_HELP_STRING([--enable-dpif-default-avx512], [Enable DPIF AVX512 implementation as default.])],
+                [dpifavx512=yes],[dpifavx512=no])
+  AC_MSG_CHECKING([whether DPIF AVX512 is default implementation])
+  if test "$dpifavx512" != yes; then
+    AC_MSG_RESULT([no])
+  else
+    OVS_CFLAGS="$OVS_CFLAGS -DDPIF_AVX512_DEFAULT"
+    AC_MSG_RESULT([yes])
+  fi
+])
+
 dnl OVS_ENABLE_WERROR
 AC_DEFUN([OVS_ENABLE_WERROR],
   [AC_ARG_ENABLE(
diff --git a/configure.ac b/configure.ac
index c077034d4..e45685a6c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -185,6 +185,7 @@ OVS_ENABLE_WERROR
 OVS_ENABLE_SPARSE
 OVS_CTAGS_IDENTIFIERS
 OVS_CHECK_DPCLS_AUTOVALIDATOR
+OVS_CHECK_DPIF_AVX512_DEFAULT
 OVS_CHECK_BINUTILS_AVX512
 
 AC_ARG_VAR(KARCH, [Kernel Architecture String])
diff --git a/lib/automake.mk b/lib/automake.mk
index 660cd07f0..49f42c2a3 100644
--- a/lib/automake.mk
+++ b/lib/automake.mk
@@ -116,6 +116,7 @@ lib_libopenvswitch_la_SOURCES = \
 	lib/dpif-netdev-private-dfc.c \
 	lib/dpif-netdev-private-dfc.h \
 	lib/dpif-netdev-private-dpcls.h \
+	lib/dpif-netdev-private-dpif.c \
 	lib/dpif-netdev-private-dpif.h \
 	lib/dpif-netdev-private-flow.h \
 	lib/dpif-netdev-private-hwol.h \
diff --git a/lib/dpif-netdev-avx512.c b/lib/dpif-netdev-avx512.c
index 0e55b0be2..f3f66fc60 100644
--- a/lib/dpif-netdev-avx512.c
+++ b/lib/dpif-netdev-avx512.c
@@ -19,6 +19,7 @@
 #if !defined(__CHECKER__)
 
 #include <config.h>
+#include <errno.h>
 
 #include "dpif-netdev.h"
 #include "dpif-netdev-perf.h"
@@ -61,6 +62,19 @@ struct dpif_userdata {
         struct pkt_flow_meta pkt_meta[NETDEV_MAX_BURST];
 };
 
+int32_t
+dp_netdev_input_outer_avx512_probe(void)
+{
+    int avx512f_available = dpdk_get_cpu_has_isa("x86_64", "avx512f");
+    int bmi2_available = dpdk_get_cpu_has_isa("x86_64", "bmi2");
+
+    if (!avx512f_available || !bmi2_available) {
+        return -ENOTSUP;
+    }
+
+    return 0;
+}
+
 int32_t
 dp_netdev_input_outer_avx512(struct dp_netdev_pmd_thread *pmd,
                              struct dp_packet_batch *packets,
diff --git a/lib/dpif-netdev-private-dpif.c b/lib/dpif-netdev-private-dpif.c
new file mode 100644
index 000000000..d829a7ee5
--- /dev/null
+++ b/lib/dpif-netdev-private-dpif.c
@@ -0,0 +1,103 @@
+/*
+ * Copyright (c) 2021 Intel Corporation.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <config.h>
+#include <errno.h>
+#include <string.h>
+
+#include "dpif-netdev-private-dpif.h"
+#include "util.h"
+#include "openvswitch/vlog.h"
+
+VLOG_DEFINE_THIS_MODULE(dpif_netdev_impl);
+
+/* Actual list of implementations goes here. */
+static struct dpif_netdev_impl_info_t dpif_impls[] = {
+    /* The default scalar C code implementation. */
+    { .func = dp_netdev_input,
+      .probe = NULL,
+      .name = "dpif_scalar", },
+
+#if (__x86_64__ && HAVE_AVX512F && HAVE_LD_AVX512_GOOD && __SSE4_2__)
+    /* Only available on x86_64 bit builds with SSE 4.2 used for OVS core. */
+    { .func = dp_netdev_input_outer_avx512,
+      .probe = dp_netdev_input_outer_avx512_probe,
+      .name = "dpif_avx512", },
+#endif
+};
+
+static dp_netdev_input_func default_dpif_func;
+
+dp_netdev_input_func
+dp_netdev_impl_get_default(void)
+{
+    /* For the first call, this will be NULL. Compute the compile time default.
+     */
+    if (!default_dpif_func) {
+        int dpif_idx = 0;
+
+/* Configure-time overriding to run test suite on all implementations. */
+#if (__x86_64__ && HAVE_AVX512F && HAVE_LD_AVX512_GOOD && __SSE4_2__)
+#ifdef DPIF_AVX512_DEFAULT
+        ovs_assert(dpif_impls[1].func == dp_netdev_input_outer_avx512);
+        if (!dp_netdev_input_outer_avx512_probe()) {
+            dpif_idx = 1;
+        };
+#endif
+#endif
+
+        VLOG_INFO("Default DPIF implementation is %s.\n",
+                  dpif_impls[dpif_idx].name);
+        default_dpif_func = dpif_impls[dpif_idx].func;
+    }
+
+    return default_dpif_func;
+}
+
+void
+dp_netdev_impl_set_default(dp_netdev_input_func func)
+{
+    default_dpif_func = func;
+}
+
+/* This function checks all available DPIF implementations, and selects the
+ * returns the function pointer to the one requested by "name".
+ */
+int32_t
+dp_netdev_impl_get_by_name(const char *name, dp_netdev_input_func *out_func)
+{
+    ovs_assert(name);
+    ovs_assert(out_func);
+
+    uint32_t i;
+
+    for (i = 0; i < ARRAY_SIZE(dpif_impls); i++) {
+        if (strcmp(dpif_impls[i].name, name) == 0) {
+            /* Probe function is optional - so check it is set before exec. */
+            if (dpif_impls[i].probe) {
+                int probe_err = dpif_impls[i].probe();
+                if (probe_err) {
+                  *out_func = NULL;
+                   return probe_err;
+                }
+            }
+            *out_func = dpif_impls[i].func;
+            return 0;
+        }
+    }
+
+    return -EINVAL;
+}
diff --git a/lib/dpif-netdev-private-dpif.h b/lib/dpif-netdev-private-dpif.h
index 2fd7cc400..a6db3c7f2 100644
--- a/lib/dpif-netdev-private-dpif.h
+++ b/lib/dpif-netdev-private-dpif.h
@@ -23,7 +23,54 @@
 struct dp_netdev_pmd_thread;
 struct dp_packet_batch;
 
-/* Available implementations for dpif work. */
+/* Typedef for DPIF functions.
+ * Returns a bitmask of packets to handle, possibly including upcall/misses.
+ */
+typedef int32_t (*dp_netdev_input_func)(struct dp_netdev_pmd_thread *pmd,
+                                        struct dp_packet_batch *packets,
+                                        odp_port_t port_no);
+
+/* Probe a DPIF implementation. This allows the implementation to validate CPU
+ * ISA availability. Returns -ENOTSUP if not available, returns 1 if valid to
+ * use.
+ */
+typedef int32_t (*dp_netdev_input_func_probe)(void);
+
+/* Structure describing each available DPIF implementation. */
+struct dpif_netdev_impl_info_t {
+    /* Function pointer to execute to have this DPIF implementation run. */
+    dp_netdev_input_func func;
+    /* Function pointer to execute to check the CPU ISA is available to run.
+     * May be NULL, which implies that it is always valid to use.
+     */
+    dp_netdev_input_func_probe probe;
+    /* Name used to select this DPIF implementation. */
+    const char *name;
+};
+
+/* This function checks all available DPIF implementations, and selects the
+ * returns the function pointer to the one requested by "name".
+ */
+int32_t
+dp_netdev_impl_get_by_name(const char *name, dp_netdev_input_func *out_func);
+
+/* Returns the default DPIF which is first ./configure selected, but can be
+ * overridden at runtime. */
+dp_netdev_input_func dp_netdev_impl_get_default(void);
+
+/* Overrides the default DPIF with the user set DPIF. */
+void dp_netdev_impl_set_default(dp_netdev_input_func func);
+
+/* Available implementations of DPIF below. */
+int32_t
+dp_netdev_input(struct dp_netdev_pmd_thread *pmd,
+                struct dp_packet_batch *packets,
+                odp_port_t in_port);
+
+/* AVX512 enabled DPIF implementation and probe functions. */
+int32_t
+dp_netdev_input_outer_avx512_probe(void);
+
 int32_t
 dp_netdev_input_outer_avx512(struct dp_netdev_pmd_thread *pmd,
                              struct dp_packet_batch *packets,
diff --git a/lib/dpif-netdev-private-thread.h b/lib/dpif-netdev-private-thread.h
index 17356d5e2..f89b1ddaa 100644
--- a/lib/dpif-netdev-private-thread.h
+++ b/lib/dpif-netdev-private-thread.h
@@ -25,6 +25,7 @@
 #include "cmap.h"
 
 #include "dpif-netdev-private-dfc.h"
+#include "dpif-netdev-private-dpif.h"
 #include "dpif-netdev-perf.h"
 #include "openvswitch/thread.h"
 
@@ -49,16 +50,6 @@ struct dp_netdev_pmd_thread_ctx {
     bool smc_enable_db;
 };
 
-/* Forward declaration for typedef. */
-struct dp_netdev_pmd_thread;
-
-/* Typedef for DPIF functions.
- * Returns a bitmask of packets to handle, possibly including upcall/misses.
- */
-typedef int32_t (*dp_netdev_input_func)(struct dp_netdev_pmd_thread *pmd,
-                                        struct dp_packet_batch *packets,
-                                        odp_port_t port_no);
-
 /* PMD: Poll modes drivers.  PMD accesses devices via polling to eliminate
  * the performance overhead of interrupt processing.  Therefore netdev can
  * not implement rx-wait for these devices.  dpif-netdev needs to poll
diff --git a/lib/dpif-netdev-unixctl.man b/lib/dpif-netdev-unixctl.man
index 858d491df..b348940b0 100644
--- a/lib/dpif-netdev-unixctl.man
+++ b/lib/dpif-netdev-unixctl.man
@@ -226,3 +226,6 @@ recirculation (only in balance-tcp mode).
 When this is the case, the above command prints the load-balancing information
 of the bonds configured in datapath \fIdp\fR showing the interface associated
 with each bucket (hash).
+.
+.IP "\fBdpif-netdev/dpif-set\fR \fIdpif_impl\fR"
+Sets the DPIF to be used to \fIdpif_impl\fR. By default "dpif_scalar" is used.
diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
index 1f15af882..9c234ef3d 100644
--- a/lib/dpif-netdev.c
+++ b/lib/dpif-netdev.c
@@ -479,8 +479,8 @@ static void dp_netdev_execute_actions(struct dp_netdev_pmd_thread *pmd,
                                       const struct flow *flow,
                                       const struct nlattr *actions,
                                       size_t actions_len);
-static int32_t dp_netdev_input(struct dp_netdev_pmd_thread *,
-                            struct dp_packet_batch *, odp_port_t port_no);
+int32_t dp_netdev_input(struct dp_netdev_pmd_thread *,
+                        struct dp_packet_batch *, odp_port_t port_no);
 static void dp_netdev_recirculate(struct dp_netdev_pmd_thread *,
                                   struct dp_packet_batch *);
 
@@ -991,6 +991,81 @@ dpif_netdev_subtable_lookup_set(struct unixctl_conn *conn, int argc,
     ds_destroy(&reply);
 }
 
+static void
+dpif_netdev_impl_set(struct unixctl_conn *conn, int argc,
+                     const char *argv[], void *aux OVS_UNUSED)
+{
+    /* This function requires just one parameter, the DPIF name.
+     * A second optional parameter can identify the datapath instance.
+     */
+    const char *dpif_name = argv[1];
+
+    static const char *error_description[2] = {
+        "Unknown DPIF implementation",
+        "CPU doesn't support the required instruction for",
+    };
+
+    dp_netdev_input_func new_func;
+    int32_t err = dp_netdev_impl_get_by_name(dpif_name, &new_func);
+    if (err) {
+        struct ds reply = DS_EMPTY_INITIALIZER;
+        ds_put_format(&reply, "DPIF implementation not available: %s %s.\n",
+                      error_description[ (err == -ENOTSUP) ], dpif_name);
+        const char *reply_str = ds_cstr(&reply);
+        unixctl_command_reply(conn, reply_str);
+        VLOG_INFO("%s", reply_str);
+        ds_destroy(&reply);
+        return;
+    }
+
+    /* argv[2] is optional datapath instance. If no datapath name is provided
+     * and only one datapath exists, the one existing datapath is reprobed.
+     */
+    ovs_mutex_lock(&dp_netdev_mutex);
+    struct dp_netdev *dp = NULL;
+
+    if (argc == 3) {
+        dp = shash_find_data(&dp_netdevs, argv[2]);
+    } else if (shash_count(&dp_netdevs) == 1) {
+        dp = shash_first(&dp_netdevs)->data;
+    }
+
+    if (!dp) {
+        ovs_mutex_unlock(&dp_netdev_mutex);
+        unixctl_command_reply_error(conn,
+                                    "please specify an existing datapath");
+        return;
+    }
+
+    /* Get PMD threads list. */
+    size_t n;
+    struct dp_netdev_pmd_thread **pmd_list;
+    sorted_poll_thread_list(dp, &pmd_list, &n);
+
+    for (size_t i = 0; i < n; i++) {
+        struct dp_netdev_pmd_thread *pmd = pmd_list[i];
+        if (pmd->core_id == NON_PMD_CORE_ID) {
+            continue;
+        }
+
+        /* Set PMD threads DPIF implementation to requested one. */
+        pmd->netdev_input_func = *new_func;
+    };
+
+    ovs_mutex_unlock(&dp_netdev_mutex);
+
+    /* Set the default implementation for PMD threads created in the future. */
+    dp_netdev_impl_set_default(*new_func);
+
+    /* Reply with success to command. */
+    struct ds reply = DS_EMPTY_INITIALIZER;
+    ds_put_format(&reply, "DPIF implementation set to %s.\n", dpif_name);
+    const char *reply_str = ds_cstr(&reply);
+    unixctl_command_reply(conn, reply_str);
+    VLOG_INFO("%s", reply_str);
+    ds_destroy(&reply);
+}
+
 static void
 dpif_netdev_pmd_rebalance(struct unixctl_conn *conn, int argc,
                           const char *argv[], void *aux OVS_UNUSED)
@@ -1213,6 +1288,10 @@ dpif_netdev_init(void)
     unixctl_command_register("dpif-netdev/subtable-lookup-prio-get", "",
                              0, 0, dpif_netdev_subtable_lookup_get,
                              NULL);
+    unixctl_command_register("dpif-netdev/dpif-set",
+                             "dpif_implementation_name [dp]",
+                             1, 2, dpif_netdev_impl_set,
+                             NULL);
     return 0;
 }
 
@@ -6067,8 +6146,8 @@ dp_netdev_configure_pmd(struct dp_netdev_pmd_thread *pmd, struct dp_netdev *dp,
     hmap_init(&pmd->send_port_cache);
     cmap_init(&pmd->tx_bonds);
 
-    /* Initialize the DPIF function pointer to the default scalar version. */
-    pmd->netdev_input_func = dp_netdev_input;
+    /* Initialize DPIF function pointer to the default configured version. */
+    pmd->netdev_input_func = dp_netdev_impl_get_default();
 
     /* init the 'flow_cache' since there is no
      * actual thread created for NON_PMD_CORE_ID. */
@@ -7002,7 +7081,7 @@ dp_netdev_input__(struct dp_netdev_pmd_thread *pmd,
     }
 }
 
-static int32_t
+int32_t
 dp_netdev_input(struct dp_netdev_pmd_thread *pmd,
                 struct dp_packet_batch *packets,
                 odp_port_t port_no)
-- 
2.32.0



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