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git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
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linux
Merge branch 'netconsole-optimize-console-registration-and-improve-testing'
Breno Leitao says:
====================
netconsole: Optimize console registration and improve testing
During performance analysis of console subsystem latency, I discovered that
netconsole registers console handlers even when no active targets exist.
These orphaned console handlers are invoked on every printk() call, get
the lock, iterate through empty target lists, and consume CPU cycles
without performing any useful work.
This patch series addresses the inefficiency by:
1. Implementing dynamic console registration/unregistration based on target
availability, ensuring console handlers are only active when needed
2. Adding automatic cleanup of unused console registrations when targets
are disabled or removed
3. Extending the selftest suite to cover non-extended console format,
which was previously untested
The optimization reduces printk() overhead by eliminating unnecessary
function calls and list traversals when netconsole targets are not
configured, improving overall system performance during heavy logging
scenarios.
v2: https://lore.kernel.org/20250602-netcons_ext-v2-0-ef88d999326d@debian.org
v1: https://lore.kernel.org/20250528-netcons_ext-v1-1-69f71e404e00@debian.org
====================
Link: https://patch.msgid.link/20250609-netcons_ext-v3-0-5336fa670326@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
+111
-31
+58
-9
drivers/net/netconsole.c
+58
-9
drivers/net/netconsole.c
···
86
86
static DEFINE_MUTEX(target_cleanup_list_lock);
87
87
88
88
/*
89
-
* Console driver for extended netconsoles. Registered on the first use to
90
-
* avoid unnecessarily enabling ext message formatting.
89
+
* Console driver for netconsoles. Register only consoles that have
90
+
* an associated target of the same type.
91
91
*/
92
-
static struct console netconsole_ext;
92
+
static struct console netconsole_ext, netconsole;
93
93
94
94
struct netconsole_target_stats {
95
95
u64_stats_t xmit_drop_count;
96
96
u64_stats_t enomem_count;
97
97
struct u64_stats_sync syncp;
98
+
};
99
+
100
+
enum console_type {
101
+
CONS_BASIC = BIT(0),
102
+
CONS_EXTENDED = BIT(1),
98
103
};
99
104
100
105
/* Features enabled in sysdata. Contrary to userdata, this data is populated by
···
460
455
return sysfs_emit(buf, "%d\n", release_enabled);
461
456
}
462
457
458
+
/* Iterate in the list of target, and make sure we don't have any console
459
+
* register without targets of the same type
460
+
*/
461
+
static void unregister_netcons_consoles(void)
462
+
{
463
+
struct netconsole_target *nt;
464
+
u32 console_type_needed = 0;
465
+
unsigned long flags;
466
+
467
+
spin_lock_irqsave(&target_list_lock, flags);
468
+
list_for_each_entry(nt, &target_list, list) {
469
+
if (nt->extended)
470
+
console_type_needed |= CONS_EXTENDED;
471
+
else
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+
console_type_needed |= CONS_BASIC;
473
+
}
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+
spin_unlock_irqrestore(&target_list_lock, flags);
475
+
476
+
if (!(console_type_needed & CONS_EXTENDED) &&
477
+
console_is_registered(&netconsole_ext))
478
+
unregister_console(&netconsole_ext);
479
+
480
+
if (!(console_type_needed & CONS_BASIC) &&
481
+
console_is_registered(&netconsole))
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+
unregister_console(&netconsole);
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+
}
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+
463
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/*
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* This one is special -- targets created through the configfs interface
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* are not enabled (and the corresponding netpoll activated) by default.
···
520
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goto out_unlock;
521
489
}
522
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523
-
if (nt->extended && !console_is_registered(&netconsole_ext))
491
+
if (nt->extended && !console_is_registered(&netconsole_ext)) {
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+
netconsole_ext.flags |= CON_ENABLED;
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register_console(&netconsole_ext);
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+
}
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+
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+
/* User might be enabling the basic format target for the very
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+
* first time, make sure the console is registered.
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+
*/
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+
if (!nt->extended && !console_is_registered(&netconsole)) {
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+
netconsole.flags |= CON_ENABLED;
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+
register_console(&netconsole);
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+
}
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/*
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505
* Skip netpoll_parse_options() -- all the attributes are
···
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list_move(&nt->list, &target_cleanup_list);
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spin_unlock_irqrestore(&target_list_lock, flags);
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mutex_unlock(&target_cleanup_list_lock);
520
+
/* Unregister consoles, whose the last target of that type got
521
+
* disabled.
522
+
*/
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+
unregister_netcons_consoles();
562
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}
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ret = strnlen(buf, count);
···
1737
1691
{
1738
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int err;
1739
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struct netconsole_target *nt, *tmp;
1694
+
u32 console_type_needed = 0;
1740
1695
unsigned int count = 0;
1741
-
bool extended = false;
1742
1696
unsigned long flags;
1743
1697
char *target_config;
1744
1698
char *input = config;
···
1754
1708
}
1755
1709
/* Dump existing printks when we register */
1756
1710
if (nt->extended) {
1757
-
extended = true;
1711
+
console_type_needed |= CONS_EXTENDED;
1758
1712
netconsole_ext.flags |= CON_PRINTBUFFER;
1759
1713
} else {
1714
+
console_type_needed |= CONS_BASIC;
1760
1715
netconsole.flags |= CON_PRINTBUFFER;
1761
1716
}
1762
1717
···
1776
1729
if (err)
1777
1730
goto undonotifier;
1778
1731
1779
-
if (extended)
1732
+
if (console_type_needed & CONS_EXTENDED)
1780
1733
register_console(&netconsole_ext);
1781
-
register_console(&netconsole);
1734
+
if (console_type_needed & CONS_BASIC)
1735
+
register_console(&netconsole);
1782
1736
pr_info("network logging started\n");
1783
1737
1784
1738
return err;
···
1809
1761
1810
1762
if (console_is_registered(&netconsole_ext))
1811
1763
unregister_console(&netconsole_ext);
1812
-
unregister_console(&netconsole);
1764
+
if (console_is_registered(&netconsole))
1765
+
unregister_console(&netconsole);
1813
1766
dynamic_netconsole_exit();
1814
1767
unregister_netdevice_notifier(&netconsole_netdev_notifier);
1815
1768
+22
-5
tools/testing/selftests/drivers/net/lib/sh/lib_netcons.sh
+22
-5
tools/testing/selftests/drivers/net/lib/sh/lib_netcons.sh
···
95
95
}
96
96
97
97
function create_dynamic_target() {
98
+
local FORMAT=${1:-"extended"}
99
+
98
100
DSTMAC=$(ip netns exec "${NAMESPACE}" \
99
101
ip link show "${DSTIF}" | awk '/ether/ {print $2}')
100
102
···
107
105
echo "${SRCIP}" > "${NETCONS_PATH}"/local_ip
108
106
echo "${DSTMAC}" > "${NETCONS_PATH}"/remote_mac
109
107
echo "${SRCIF}" > "${NETCONS_PATH}"/dev_name
108
+
109
+
if [ "${FORMAT}" == "basic" ]
110
+
then
111
+
# Basic target does not support release
112
+
echo 0 > "${NETCONS_PATH}"/release
113
+
echo 0 > "${NETCONS_PATH}"/extended
114
+
elif [ "${FORMAT}" == "extended" ]
115
+
then
116
+
echo 1 > "${NETCONS_PATH}"/extended
117
+
fi
110
118
111
119
echo 1 > "${NETCONS_PATH}"/enabled
112
120
}
···
171
159
172
160
function validate_result() {
173
161
local TMPFILENAME="$1"
162
+
local FORMAT=${2:-"extended"}
174
163
175
164
# TMPFILENAME will contain something like:
176
165
# 6.11.1-0_fbk0_rc13_509_g30d75cea12f7,13,1822,115075213798,-;netconsole selftest: netcons_gtJHM
···
189
176
exit "${ksft_fail}"
190
177
fi
191
178
192
-
if ! grep -q "${USERDATA_KEY}=${USERDATA_VALUE}" "${TMPFILENAME}"; then
193
-
echo "FAIL: ${USERDATA_KEY}=${USERDATA_VALUE} not found in ${TMPFILENAME}" >&2
194
-
cat "${TMPFILENAME}" >&2
195
-
exit "${ksft_fail}"
179
+
# userdata is not supported on basic format target,
180
+
# thus, do not validate it.
181
+
if [ "${FORMAT}" != "basic" ];
182
+
then
183
+
if ! grep -q "${USERDATA_KEY}=${USERDATA_VALUE}" "${TMPFILENAME}"; then
184
+
echo "FAIL: ${USERDATA_KEY}=${USERDATA_VALUE} not found in ${TMPFILENAME}" >&2
185
+
cat "${TMPFILENAME}" >&2
186
+
exit "${ksft_fail}"
187
+
fi
196
188
fi
197
189
198
190
# Delete the file once it is validated, otherwise keep it
199
191
# for debugging purposes
200
192
rm "${TMPFILENAME}"
201
-
exit "${ksft_pass}"
202
193
}
203
194
204
195
function check_for_dependencies() {
+31
-17
tools/testing/selftests/drivers/net/netcons_basic.sh
+31
-17
tools/testing/selftests/drivers/net/netcons_basic.sh
···
32
32
echo "6 5" > /proc/sys/kernel/printk
33
33
# Remove the namespace, interfaces and netconsole target on exit
34
34
trap cleanup EXIT
35
-
# Create one namespace and two interfaces
36
-
set_network
37
-
# Create a dynamic target for netconsole
38
-
create_dynamic_target
39
-
# Set userdata "key" with the "value" value
40
-
set_user_data
41
-
# Listed for netconsole port inside the namespace and destination interface
42
-
listen_port_and_save_to "${OUTPUT_FILE}" &
43
-
# Wait for socat to start and listen to the port.
44
-
wait_local_port_listen "${NAMESPACE}" "${PORT}" udp
45
-
# Send the message
46
-
echo "${MSG}: ${TARGET}" > /dev/kmsg
47
-
# Wait until socat saves the file to disk
48
-
busywait "${BUSYWAIT_TIMEOUT}" test -s "${OUTPUT_FILE}"
49
35
50
-
# Make sure the message was received in the dst part
51
-
# and exit
52
-
validate_result "${OUTPUT_FILE}"
36
+
# Run the test twice, with different format modes
37
+
for FORMAT in "basic" "extended"
38
+
do
39
+
echo "Running with target mode: ${FORMAT}"
40
+
# Create one namespace and two interfaces
41
+
set_network
42
+
# Create a dynamic target for netconsole
43
+
create_dynamic_target "${FORMAT}"
44
+
# Only set userdata for extended format
45
+
if [ "$FORMAT" == "extended" ]
46
+
then
47
+
# Set userdata "key" with the "value" value
48
+
set_user_data
49
+
fi
50
+
# Listed for netconsole port inside the namespace and destination interface
51
+
listen_port_and_save_to "${OUTPUT_FILE}" &
52
+
# Wait for socat to start and listen to the port.
53
+
wait_local_port_listen "${NAMESPACE}" "${PORT}" udp
54
+
# Send the message
55
+
echo "${MSG}: ${TARGET}" > /dev/kmsg
56
+
# Wait until socat saves the file to disk
57
+
busywait "${BUSYWAIT_TIMEOUT}" test -s "${OUTPUT_FILE}"
58
+
59
+
# Make sure the message was received in the dst part
60
+
# and exit
61
+
validate_result "${OUTPUT_FILE}" "${FORMAT}"
62
+
cleanup
63
+
done
64
+
65
+
trap - EXIT
66
+
exit "${ksft_pass}"