[ovs-dev] [v10 03/12] dpif-netdev: Add study function to select the best mfex function
Kumar Amber
kumar.amber at intel.com
Tue Jul 13 05:32:34 UTC 2021
The study function runs all the available implementations
of miniflow_extract and makes a choice whose hitmask has
maximum hits and sets the mfex to that function.
Study can be run at runtime using the following command:
$ ovs-appctl dpif-netdev/miniflow-parser-set study
Signed-off-by: Kumar Amber <kumar.amber at intel.com>
Co-authored-by: Harry van Haaren <harry.van.haaren at intel.com>
Signed-off-by: Harry van Haaren <harry.van.haaren at intel.com>
Acked-by: Eelco Chaudron <echaudro at redhat.com>
---
v10:
- fix minor comments from Eelco
v9:
- fix comments Flavio
v8:
- fix review comments Flavio
v7:
- fix review comments(Eelco)
v5:
- fix review comments(Ian, Flavio, Eelco)
- add Atomic set in study
---
---
NEWS | 3 +
lib/automake.mk | 1 +
lib/dpif-netdev-extract-study.c | 136 ++++++++++++++++++++++++++++++
lib/dpif-netdev-private-extract.c | 12 +++
lib/dpif-netdev-private-extract.h | 19 +++++
5 files changed, 171 insertions(+)
create mode 100644 lib/dpif-netdev-extract-study.c
diff --git a/NEWS b/NEWS
index cf254bcfe..4a7b89409 100644
--- a/NEWS
+++ b/NEWS
@@ -35,6 +35,9 @@ Post-v2.15.0
* Add command line option to switch between MFEX function pointers.
* Add miniflow extract auto-validator function to compare different
miniflow extract implementations against default implementation.
+ * Add study function to miniflow function table which studies packet
+ and automatically chooses the best miniflow implementation for that
+ traffic.
- ovs-ctl:
* New option '--no-record-hostname' to disable hostname configuration
in ovsdb on startup.
diff --git a/lib/automake.mk b/lib/automake.mk
index 53b8abc0f..f4f36325e 100644
--- a/lib/automake.mk
+++ b/lib/automake.mk
@@ -107,6 +107,7 @@ lib_libopenvswitch_la_SOURCES = \
lib/dp-packet.h \
lib/dp-packet.c \
lib/dpdk.h \
+ lib/dpif-netdev-extract-study.c \
lib/dpif-netdev-lookup.h \
lib/dpif-netdev-lookup.c \
lib/dpif-netdev-lookup-autovalidator.c \
diff --git a/lib/dpif-netdev-extract-study.c b/lib/dpif-netdev-extract-study.c
new file mode 100644
index 000000000..eddb35682
--- /dev/null
+++ b/lib/dpif-netdev-extract-study.c
@@ -0,0 +1,136 @@
+/*
+ * Copyright (c) 2021 Intel.
+ *
+ * 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 <stdint.h>
+#include <string.h>
+
+#include "dpif-netdev-private-thread.h"
+#include "openvswitch/vlog.h"
+#include "ovs-thread.h"
+
+VLOG_DEFINE_THIS_MODULE(dpif_mfex_extract_study);
+
+static atomic_uint32_t mfex_study_pkts_count = 0;
+
+/* Struct to hold miniflow study stats. */
+struct study_stats {
+ uint32_t pkt_count;
+ uint32_t impl_hitcount[MFEX_IMPL_MAX];
+};
+
+/* Define per thread data to hold the study stats. */
+DEFINE_PER_THREAD_MALLOCED_DATA(struct study_stats *, study_stats);
+
+/* Allocate per thread PMD pointer space for study_stats. */
+static inline struct study_stats *
+mfex_study_get_study_stats_ptr(void)
+{
+ struct study_stats *stats = study_stats_get();
+ if (OVS_UNLIKELY(!stats)) {
+ stats = xzalloc(sizeof *stats);
+ study_stats_set_unsafe(stats);
+ }
+ return stats;
+}
+
+uint32_t
+mfex_study_traffic(struct dp_packet_batch *packets,
+ struct netdev_flow_key *keys,
+ uint32_t keys_size, odp_port_t in_port,
+ struct dp_netdev_pmd_thread *pmd_handle)
+{
+ uint32_t hitmask = 0;
+ uint32_t mask = 0;
+ struct dp_netdev_pmd_thread *pmd = pmd_handle;
+ struct dpif_miniflow_extract_impl *miniflow_funcs;
+ struct study_stats *stats = mfex_study_get_study_stats_ptr();
+ miniflow_funcs = dpif_mfex_impl_info_get();
+
+ /* Run traffic optimized miniflow_extract to collect the hitmask
+ * to be compared after certain packets have been hit to choose
+ * the best miniflow_extract version for that traffic.
+ */
+ for (int i = MFEX_IMPL_START_IDX; i < MFEX_IMPL_MAX; i++) {
+ if (!miniflow_funcs[i].available) {
+ continue;
+ }
+
+ hitmask = miniflow_funcs[i].extract_func(packets, keys, keys_size,
+ in_port, pmd_handle);
+ stats->impl_hitcount[i] += count_1bits(hitmask);
+
+ /* If traffic is not classified then we dont overwrite the keys
+ * array in minfiflow implementations so its safe to create a
+ * mask for all those packets whose miniflow have been created.
+ */
+ mask |= hitmask;
+ }
+
+ stats->pkt_count += dp_packet_batch_size(packets);
+
+ /* Choose the best implementation after a minimum packets have been
+ * processed.
+ */
+ if (stats->pkt_count >= MFEX_MAX_PKT_COUNT) {
+ uint32_t best_func_index = MFEX_IMPL_START_IDX;
+ uint32_t max_hits = 0;
+ for (int i = MFEX_IMPL_START_IDX; i < MFEX_IMPL_MAX; i++) {
+ if (stats->impl_hitcount[i] > max_hits) {
+ max_hits = stats->impl_hitcount[i];
+ best_func_index = i;
+ }
+ }
+
+ /* If 50% of the packets hit, enable the function. */
+ if (max_hits >= (mfex_study_pkts_count / 2)) {
+ miniflow_extract_func mf_func =
+ miniflow_funcs[best_func_index].extract_func;
+ atomic_uintptr_t *pmd_func = (void *)&pmd->miniflow_extract_opt;
+ atomic_store_relaxed(pmd_func, (uintptr_t) mf_func);
+ VLOG_INFO("MFEX study chose impl %s: (hits %u/%u pkts)",
+ miniflow_funcs[best_func_index].name, max_hits,
+ stats->pkt_count);
+ } else {
+ /* Set the implementation to null for default miniflow. */
+ miniflow_extract_func mf_func =
+ miniflow_funcs[MFEX_IMPL_SCALAR].extract_func;
+ atomic_uintptr_t *pmd_func = (void *)&pmd->miniflow_extract_opt;
+ atomic_store_relaxed(pmd_func, (uintptr_t) mf_func);
+ VLOG_INFO("Not enough packets matched (%d/%d), disabling"
+ " optimized MFEX.", max_hits, stats->pkt_count);
+ }
+
+ /* In debug mode show stats for all the counters. */
+ if (VLOG_IS_DBG_ENABLED()) {
+
+ for (int i = MFEX_IMPL_START_IDX; i < MFEX_IMPL_MAX; i++) {
+ VLOG_DBG("MFEX study results for implementation %s:"
+ " (hits %d/%d pkts)",
+ miniflow_funcs[i].name, stats->impl_hitcount[i],
+ stats->pkt_count);
+ }
+ }
+
+ /* Reset stats so that study function can be called again
+ * for next traffic type and optimal function ptr can be
+ * chosen.
+ */
+ memset(stats, 0, sizeof(struct study_stats));
+ }
+ return mask;
+}
diff --git a/lib/dpif-netdev-private-extract.c b/lib/dpif-netdev-private-extract.c
index 6c5afd13d..64745f66c 100644
--- a/lib/dpif-netdev-private-extract.c
+++ b/lib/dpif-netdev-private-extract.c
@@ -47,6 +47,11 @@ static struct dpif_miniflow_extract_impl mfex_impls[] = {
.probe = NULL,
.extract_func = NULL,
.name = "scalar", },
+
+ [MFEX_IMPL_STUDY] = {
+ .probe = NULL,
+ .extract_func = mfex_study_traffic,
+ .name = "study", },
};
BUILD_ASSERT_DECL(MFEX_IMPL_MAX == ARRAY_SIZE(mfex_impls));
@@ -161,6 +166,13 @@ dp_mfex_impl_get_by_name(const char *name, miniflow_extract_func *out_func)
return -ENOENT;
}
+struct dpif_miniflow_extract_impl *
+dpif_mfex_impl_info_get(void) {
+
+ return mfex_impls;
+
+}
+
uint32_t
dpif_miniflow_extract_autovalidator(struct dp_packet_batch *packets,
struct netdev_flow_key *keys,
diff --git a/lib/dpif-netdev-private-extract.h b/lib/dpif-netdev-private-extract.h
index 88c517506..9c03a1aa0 100644
--- a/lib/dpif-netdev-private-extract.h
+++ b/lib/dpif-netdev-private-extract.h
@@ -80,6 +80,7 @@ struct dpif_miniflow_extract_impl {
enum dpif_miniflow_extract_impl_idx {
MFEX_IMPL_AUTOVALIDATOR,
MFEX_IMPL_SCALAR,
+ MFEX_IMPL_STUDY,
MFEX_IMPL_MAX
};
@@ -91,6 +92,9 @@ extern struct ovs_mutex dp_netdev_mutex;
#define MFEX_IMPL_START_IDX MFEX_IMPL_MAX
+/* Max count of packets to be compared. */
+#define MFEX_MAX_PKT_COUNT (128)
+
/* This function returns all available implementations to the caller. The
* quantity of implementations is returned by the int return value.
*/
@@ -111,6 +115,9 @@ miniflow_extract_func dp_mfex_impl_get_default(void);
/* Overrides the default MFEX with the user set MFEX. */
int dp_mfex_impl_set_default_by_name(const char *name);
+/* Retrieve the array of miniflow implementations for iteration. */
+struct dpif_miniflow_extract_impl *
+dpif_mfex_impl_info_get(void);
/* Initializes the available miniflow extract implementations by probing for
* the CPU ISA requirements. As the runtime available CPU ISA does not change
@@ -132,4 +139,16 @@ dpif_miniflow_extract_autovalidator(struct dp_packet_batch *batch,
uint32_t keys_size, odp_port_t in_port,
struct dp_netdev_pmd_thread *pmd_handle);
+/* Retrieve the number of packets by studying packets using different miniflow
+ * implementations to choose the best implementation using the maximum hitmask
+ * count.
+ * On error, returns a zero for no packets.
+ * On success, returns mask of the packets hit.
+ */
+uint32_t
+mfex_study_traffic(struct dp_packet_batch *packets,
+ struct netdev_flow_key *keys,
+ uint32_t keys_size, odp_port_t in_port,
+ struct dp_netdev_pmd_thread *pmd_handle);
+
#endif /* MFEX_AVX512_EXTRACT */
--
2.25.1
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