bpftune: support rollback mode (-R) for bpftune

Support rollback mode where if bpftune is run with -R option, we roll back
sysctl settings on exit.  Log will show us a summary of changes along with
the values were rolled back; for example:

Aug 23 19:15:04 bpf bpftune[360835]: sysctl 'net.ipv4.tcp_wmem' changed from (4096 16384 16384 ) -> (4096 16384 2220415 )
Aug 23 19:15:04 bpf bpftune[360835]: Scenario 'need to increase TCP buffer size(s)' occurred for tunable 'net.ipv4.tcp_wmem' in global ns. Need to increase buffer size(s) to maximize throughput
Aug 23 19:15:04 bpf bpftune[360835]: Rolling back sysctl values for 'net.ipv4.tcp_wmem' from (4096 16384 2220415 ) to original values (4096 16384 16384 )...

Signed-off-by: Alan Maguire <[email protected]>

docs/bpftune.rst

@@ -16,6 +16,7 @@ SYNOPSIS
 	| { [**-s** | **--stderr** } | { [**-c** | **--cgroup**] cgroup} |
         { [**-l** | **--libdir** ] libdir} | [{ **-d** | **--debug** }] }
         { [**-r** | **--learning_rate** ] learning_rate}
+        { [**-R** | **--rollback** ]}
         { [**-S** | **--support** ]}
 
 DESCRIPTION
@@ -75,5 +76,12 @@ OPTIONS
                 the limit is increased by 25%.  Default learning rate is 4.
                 Lower values are more conservative as they change only when
                 closer to limits, but may require more frequent changes as
-                a result
+                a result.
 
+        -R, --rollback
+
+                Roll back sysctl settings on exit; this allows us to explore
+                tunable updates bpftune makes without making long-term changes
+                to the system.  On exit, bpftune summarizes the changes made
+                and rolls back to the sysctl values that were set prior to
+                bpftune running.

include/bpftune/bpftune.h

@@ -167,7 +167,7 @@ struct bpftuner {
 	const char *name;
 	struct bpf_object_skeleton *skeleton;
 	enum bpftune_support_level bpf_support;
-	bool bpf_legacy;
+	bool rollback;
 	void *skel;
 	void *obj;
 	int (*init)(struct bpftuner *tuner);

include/bpftune/libbpftune.h

@@ -299,4 +299,6 @@ int bpftuner_strategies_add(struct bpftuner *tuner, struct bpftuner_strategy **s
 bool bpftuner_bpf_prog_in_strategy(struct bpftuner *tuner, const char *prog);
 void bpftuner_bpf_set_autoload(struct bpftuner *tuner);
 
+void bpftuner_rollback_set(struct bpftuner *tuner);
+
 #endif /* __LIBBPFTUNE_H */

src/bpftune.c

@@ -54,6 +54,7 @@
 int ringbuf_map_fd;
 void *ring_buffer;
 bool use_stderr;
+bool rollback;
 
 char *allowlist[BPFTUNE_MAX_TUNERS];
 int nr_allowlist;
@@ -200,6 +201,8 @@ int init(const char *library_dir)
 		/* individual tuner failure shouldn't prevent progress */
 		if (!tuner)
 			continue;
+		if (rollback)
+			bpftuner_rollback_set(tuner);
 		if (ringbuf_map_fd == 0)
 			ringbuf_map_fd = bpftuner_ring_buffer_map_fd(tuner);
 	}
@@ -233,6 +236,7 @@ void do_help(void)
 		"		     { -h|--help}}\n"
 		"		     { -l|--library_path library_path}\n"
 		"		     { -r|--learning_rate learning_rate}\n"
+		"		     { -R|--rollback}\n"
 		"		     { -s|--stderr}\n"
 		"		     { -S|--suppport}\n"
 		"		     { -V|--version}}\n",
@@ -284,6 +288,7 @@ int main(int argc, char *argv[])
 		{ "help",	no_argument,		NULL,	'h' },
 		{ "libdir",	required_argument,	NULL,	'l' },
 		{ "learning_rate", required_argument,	NULL,	'r' },
+		{ "rollback",	no_argument,		NULL,	'R' },
 		{ "stderr", 	no_argument,		NULL,	's' },
 		{ "support",	no_argument,		NULL,	'S' },
 		{ "version",	no_argument,		NULL,	'V' },
@@ -302,7 +307,7 @@ int main(int argc, char *argv[])
 
 	bin_name = argv[0];
 
-	while ((opt = getopt_long(argc, argv, "a:c:dDhl:Lr:sSV", options, NULL))
+	while ((opt = getopt_long(argc, argv, "a:c:dDhl:Lr:RsSV", options, NULL))
 		>= 0) {
 		switch (opt) {
 		case 'a':
@@ -338,6 +343,9 @@ int main(int argc, char *argv[])
 				return 1;
 			}
 			break;
+		case 'R':
+			rollback = true;
+			break;
 		case 's':
 			use_stderr = true;
 			break;

src/libbpftune.c

@@ -1055,6 +1055,18 @@ static void bpftuner_scenario_log(struct bpftuner *tuner, unsigned int tunable,
 			}
 			bpftune_log(BPFTUNE_LOG_LEVEL, "sysctl '%s' changed from (%s) -> (%s)\n",
 				    t->desc.name, oldvals, newvals);
+
+			if (tuner->rollback && global_ns) {
+				bpftuner_tunable_sysctl_write(tuner,
+					tunable,
+					scenario,
+					0,
+					t->desc.num_values,
+					t->initial_values,
+					"Rolling back sysctl values for '%s' from (%s) to original values (%s)...\n",
+					t->desc.name,
+					newvals, oldvals);
+			}
 		}
 	} else {
 		bpftune_log(BPFTUNE_LOG_LEVEL, "Scenario '%s' occurred for tunable '%s' in %sglobal ns. %s\n",
@@ -1677,3 +1689,8 @@ void bpftuner_bpf_set_autoload(struct bpftuner *tuner)
 		}
 	}
 }
+
+void bpftuner_rollback_set(struct bpftuner *tuner)
+{
+	tuner->rollback = true;
+}

src/libbpftune.map

@@ -42,6 +42,7 @@ LIBBPFTUNE_0.1.1 {
 	        bpftuner_ring_buffer_map_fd;
 		bpftuner_strategy_set;
 		bpftuner_strategies_add;
+		bpftuner_rollback_set;
 		bpftune_ring_buffer_init;
 		bpftune_ring_buffer_poll;
 		bpftune_ring_buffer_fini;

test/Makefile

@@ -23,6 +23,7 @@ PERF_TESTS = iperf3_test qperf_test
 TUNER_TESTS =	support_test log_test service_test inotify_test cap_test \
 		sample_test sample_legacy_test \
 		strategy_test strategy_legacy_test \
+		rollback_test rollback_legacy_test \
 		sysctl_test sysctl_legacy_test sysctl_netns_test \
 		netns_test netns_legacy_test \
 		backlog_test backlog_legacy_test \

test/rollback_legacy_test.sh

@@ -0,0 +1,124 @@
+#!/usr/bin/bash
+#
+# SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note
+#
+# Copyright (c) 2023, Oracle and/or its affiliates.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public
+# License v2 as published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public
+# License along with this program; if not, write to the
+# Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+# Boston, MA 021110-1307, USA.
+#
+
+# run iperf3 test with low wmem max, ensure tuner increases it but it is
+# rolled back on exit.
+
+PORT=5201
+
+. ./test_lib.sh
+
+SLEEPTIME=1
+TIMEOUT=30
+
+for FAMILY in ipv4 ipv6 ; do
+
+ for CLIENT_OPTS in "" ; do
+   case $FAMILY in
+   ipv4)
+   	ADDR=$VETH1_IPV4
+	;;
+   ipv6)
+	ADDR=$VETH1_IPV6
+	;;
+   esac
+
+   test_start "$0|rollback legacy test to $ADDR:$PORT $FAMILY opts $CLIENT_OPTS $LATENCY"
+
+   wmem_orig=($(sysctl -n net.ipv4.tcp_wmem))
+
+   test_setup true
+
+   sysctl -w net.ipv4.tcp_wmem="${wmem_orig[0]} ${wmem_orig[1]} ${wmem_orig[1]}"
+
+   declare -A results
+   for MODE in baseline test ; do
+
+	echo "Running ${MODE}..."
+	test_run_cmd_local "ip netns exec $NETNS $IPERF3 -s -p $PORT -1 &"
+	if [[ $MODE != "baseline" ]]; then
+		test_run_cmd_local "$BPFTUNE -LR &"
+		sleep $SETUPTIME
+	else
+		LOGSZ=$(wc -l $LOGFILE | awk '{print $1}')
+		LOGSZ=$(expr $LOGSZ + 1)
+	fi
+	test_run_cmd_local "$IPERF3 -fm $CLIENT_OPTS -p $PORT -c $ADDR" true
+
+	sleep $SLEEPTIME
+
+	sresults=$(grep -E "sender" ${CMDLOG} | awk '{print $7}')
+	rresults=$(grep -E "receiver" ${CMDLOG} | awk '{print $7}')
+	units=$(grep -E "sender|receiver" ${CMDLOG} | awk '{print $8}' |head -1)
+
+	if [[ $MODE == "baseline" ]]; then
+                read -r -a sbaseline_results <<< $sresults
+		read -r -a rbaseline_results <<< $rresults
+                echo "" > ${CMDLOG}
+        else
+                read -r -a stest_results <<< $sresults
+		read -r -a rtest_results <<< $rresults
+		pkill -TERM bpftune
+        fi
+	sleep $SLEEPTIME
+   done
+
+   wmem_post=($(sysctl -n net.ipv4.tcp_wmem))
+   sysctl -w net.ipv4.tcp_wmem="${wmem_orig[0]} ${wmem_orig[1]} ${wmem_orig[2]}"
+   if [[ $MODE == "test" ]]; then
+	if [[ "${wmem_post[2]}" -eq ${wmem_orig[1]} ]]; then
+		echo "wmem before ${wmem_orig[1]} ; after ${wmem_post[2]}"
+	else
+		test_cleanup
+	fi
+   fi
+   printf "Results sender (${units}): "
+   for (( i=0; i < ${#sbaseline_results[@]}; i++ ))
+   do
+	sbase=$(roundup ${sbaseline_results[$i]})
+	stest=$(roundup ${stest_results[$i]})
+	if [[ ${sbase} -gt ${stest} ]]; then  
+		bold "Warning: baseline (${sbase}) > test (${stest})"
+	else
+		echo "baseline (${sbase}) < test (${stest})"
+	fi
+   done
+   printf "Results receiver (${units}): "
+   for (( i=0; i < ${#rbaseline_results[@]}; i++ ))
+   do
+	rbase=$(roundup ${rbaseline_results[$i]})
+	rtest=$(roundup ${rtest_results[$i]})
+	if [[ ${rbase} -gt ${rtest} ]]; then
+                bold "Warning: baseline (${rbase}) > test (${rtest})"
+	else
+		echo "baseline (${rbase}) < test (${rtest})"
+	fi
+   done 
+
+   grep "Rolling back" $LOGFILE
+
+   test_pass
+
+   test_cleanup
+ done
+done
+
+test_exit

test/rollback_test.sh

@@ -0,0 +1,124 @@
+#!/usr/bin/bash
+#
+# SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note
+#
+# Copyright (c) 2023, Oracle and/or its affiliates.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public
+# License v2 as published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public
+# License along with this program; if not, write to the
+# Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+# Boston, MA 021110-1307, USA.
+#
+
+# run iperf3 test with low wmem max, ensure tuner increases it but it is
+# rolled back on exit.
+
+PORT=5201
+
+. ./test_lib.sh
+
+SLEEPTIME=1
+TIMEOUT=30
+
+for FAMILY in ipv4 ipv6 ; do
+
+ for CLIENT_OPTS in "" ; do
+   case $FAMILY in
+   ipv4)
+   	ADDR=$VETH1_IPV4
+	;;
+   ipv6)
+	ADDR=$VETH1_IPV6
+	;;
+   esac
+
+   test_start "$0|rollback test to $ADDR:$PORT $FAMILY opts $CLIENT_OPTS $LATENCY"
+
+   wmem_orig=($(sysctl -n net.ipv4.tcp_wmem))
+
+   test_setup true
+
+   sysctl -w net.ipv4.tcp_wmem="${wmem_orig[0]} ${wmem_orig[1]} ${wmem_orig[1]}"
+
+   declare -A results
+   for MODE in baseline test ; do
+
+	echo "Running ${MODE}..."
+	test_run_cmd_local "ip netns exec $NETNS $IPERF3 -s -p $PORT -1 &"
+	if [[ $MODE != "baseline" ]]; then
+		test_run_cmd_local "$BPFTUNE -R &"
+		sleep $SETUPTIME
+	else
+		LOGSZ=$(wc -l $LOGFILE | awk '{print $1}')
+		LOGSZ=$(expr $LOGSZ + 1)
+	fi
+	test_run_cmd_local "$IPERF3 -fm $CLIENT_OPTS -p $PORT -c $ADDR" true
+
+	sleep $SLEEPTIME
+
+	sresults=$(grep -E "sender" ${CMDLOG} | awk '{print $7}')
+	rresults=$(grep -E "receiver" ${CMDLOG} | awk '{print $7}')
+	units=$(grep -E "sender|receiver" ${CMDLOG} | awk '{print $8}' |head -1)
+
+	if [[ $MODE == "baseline" ]]; then
+                read -r -a sbaseline_results <<< $sresults
+		read -r -a rbaseline_results <<< $rresults
+                echo "" > ${CMDLOG}
+        else
+                read -r -a stest_results <<< $sresults
+		read -r -a rtest_results <<< $rresults
+		pkill -TERM bpftune
+        fi
+	sleep $SLEEPTIME
+   done
+
+   wmem_post=($(sysctl -n net.ipv4.tcp_wmem))
+   sysctl -w net.ipv4.tcp_wmem="${wmem_orig[0]} ${wmem_orig[1]} ${wmem_orig[2]}"
+   if [[ $MODE == "test" ]]; then
+	if [[ "${wmem_post[2]}" -eq ${wmem_orig[1]} ]]; then
+		echo "wmem before ${wmem_orig[1]} ; after ${wmem_post[2]}"
+	else
+		test_cleanup
+	fi
+   fi
+   printf "Results sender (${units}): "
+   for (( i=0; i < ${#sbaseline_results[@]}; i++ ))
+   do
+	sbase=$(roundup ${sbaseline_results[$i]})
+	stest=$(roundup ${stest_results[$i]})
+	if [[ ${sbase} -gt ${stest} ]]; then  
+		bold "Warning: baseline (${sbase}) > test (${stest})"
+	else
+		echo "baseline (${sbase}) < test (${stest})"
+	fi
+   done
+   printf "Results receiver (${units}): "
+   for (( i=0; i < ${#rbaseline_results[@]}; i++ ))
+   do
+	rbase=$(roundup ${rbaseline_results[$i]})
+	rtest=$(roundup ${rtest_results[$i]})
+	if [[ ${rbase} -gt ${rtest} ]]; then
+                bold "Warning: baseline (${rbase}) > test (${rtest})"
+	else
+		echo "baseline (${rbase}) < test (${rtest})"
+	fi
+   done 
+
+   grep "Rolling back" $LOGFILE
+
+   test_pass
+
+   test_cleanup
+ done
+done
+
+test_exit