Merge pull request #1239 from poettering/cgroup-pids

core: add support for the "pids" cgroup controller

15 files changed, 332 insertions, 70 deletions

diff --git a/src/basic/cgroup-util.c b/src/basic/cgroup-util.c
index 94a25585b2..6099dc8721 100644
--- a/src/basic/cgroup-util.c
+++ b/src/basic/cgroup-util.c
@@ -2018,9 +2018,10 @@ int cg_mask_supported(CGroupMask *ret) {
                         mask |= CGROUP_CONTROLLER_TO_MASK(v);
                 }
 
-                /* Currently, we only support the memory controller in
-                 * the unified hierarchy, mask everything else off. */
-                mask &= CGROUP_MASK_MEMORY;
+                /* Currently, we only support the memory and pids
+                 * controller in the unified hierarchy, mask
+                 * everything else off. */
+                mask &= CGROUP_MASK_MEMORY | CGROUP_MASK_PIDS;
 
         } else {
                 CGroupController c;
@@ -2212,6 +2213,7 @@ static const char *cgroup_controller_table[_CGROUP_CONTROLLER_MAX] = {
         [CGROUP_CONTROLLER_BLKIO] = "blkio",
         [CGROUP_CONTROLLER_MEMORY] = "memory",
         [CGROUP_CONTROLLER_DEVICES] = "devices",
+        [CGROUP_CONTROLLER_PIDS] = "pids",
 };
 
 DEFINE_STRING_TABLE_LOOKUP(cgroup_controller, CGroupController);
diff --git a/src/basic/cgroup-util.h b/src/basic/cgroup-util.h
index 16d439fd9d..7e1b4f9c72 100644
--- a/src/basic/cgroup-util.h
+++ b/src/basic/cgroup-util.h
@@ -35,6 +35,7 @@ typedef enum CGroupController {
         CGROUP_CONTROLLER_BLKIO,
         CGROUP_CONTROLLER_MEMORY,
         CGROUP_CONTROLLER_DEVICES,
+        CGROUP_CONTROLLER_PIDS,
         _CGROUP_CONTROLLER_MAX,
         _CGROUP_CONTROLLER_INVALID = -1,
 } CGroupController;
@@ -48,6 +49,7 @@ typedef enum CGroupMask {
         CGROUP_MASK_BLKIO = CGROUP_CONTROLLER_TO_MASK(CGROUP_CONTROLLER_BLKIO),
         CGROUP_MASK_MEMORY = CGROUP_CONTROLLER_TO_MASK(CGROUP_CONTROLLER_MEMORY),
         CGROUP_MASK_DEVICES = CGROUP_CONTROLLER_TO_MASK(CGROUP_CONTROLLER_DEVICES),
+        CGROUP_MASK_PIDS = CGROUP_CONTROLLER_TO_MASK(CGROUP_CONTROLLER_PIDS),
         _CGROUP_MASK_ALL = CGROUP_CONTROLLER_TO_MASK(_CGROUP_CONTROLLER_MAX) - 1
 } CGroupMask;
 
diff --git a/src/cgtop/cgtop.c b/src/cgtop/cgtop.c
index f26aeb39df..4786a155da 100644
--- a/src/cgtop/cgtop.c
+++ b/src/cgtop/cgtop.c
@@ -45,7 +45,7 @@ typedef struct Group {
         bool memory_valid:1;
         bool io_valid:1;
 
-        unsigned n_tasks;
+        uint64_t n_tasks;
 
         unsigned cpu_iteration;
         nsec_t cpu_usage;
@@ -65,7 +65,12 @@ static unsigned arg_iterations = (unsigned) -1;
 static bool arg_batch = false;
 static bool arg_raw = false;
 static usec_t arg_delay = 1*USEC_PER_SEC;
-static bool arg_kernel_threads = false;
+
+enum {
+        COUNT_PIDS,
+        COUNT_USERSPACE_PROCESSES,
+        COUNT_ALL_PROCESSES,
+} arg_count = COUNT_PIDS;
 static bool arg_recursive = true;
 
 static enum {
@@ -73,7 +78,7 @@ static enum {
         ORDER_TASKS,
         ORDER_CPU,
         ORDER_MEMORY,
-        ORDER_IO
+        ORDER_IO,
 } arg_order = ORDER_CPU;
 
 static enum {
@@ -153,7 +158,7 @@ static int process(
                 }
         }
 
-        if (streq(controller, SYSTEMD_CGROUP_CONTROLLER)) {
+        if (streq(controller, SYSTEMD_CGROUP_CONTROLLER) && IN_SET(arg_count, COUNT_ALL_PROCESSES, COUNT_USERSPACE_PROCESSES)) {
                 _cleanup_fclose_ FILE *f = NULL;
                 pid_t pid;
 
@@ -166,7 +171,7 @@ static int process(
                 g->n_tasks = 0;
                 while (cg_read_pid(f, &pid) > 0) {
 
-                        if (!arg_kernel_threads && is_kernel_thread(pid) > 0)
+                        if (arg_count == COUNT_USERSPACE_PROCESSES && is_kernel_thread(pid) > 0)
                                 continue;
 
                         g->n_tasks++;
@@ -175,6 +180,26 @@ static int process(
                 if (g->n_tasks > 0)
                         g->n_tasks_valid = true;
 
+        } else if (streq(controller, "pids") && arg_count == COUNT_PIDS) {
+                _cleanup_free_ char *p = NULL, *v = NULL;
+
+                r = cg_get_path(controller, path, "pids.current", &p);
+                if (r < 0)
+                        return r;
+
+                r = read_one_line_file(p, &v);
+                if (r == -ENOENT)
+                        return 0;
+                if (r < 0)
+                        return r;
+
+                r = safe_atou64(v, &g->n_tasks);
+                if (r < 0)
+                        return r;
+
+                if (g->n_tasks > 0)
+                        g->n_tasks_valid = true;
+
         } else if (streq(controller, "cpuacct") && cg_unified() <= 0) {
                 _cleanup_free_ char *p = NULL, *v = NULL;
                 uint64_t new_usage;
@@ -371,6 +396,7 @@ static int refresh_one(
                         return r;
 
                 if (arg_recursive &&
+                    IN_SET(arg_count, COUNT_ALL_PROCESSES, COUNT_USERSPACE_PROCESSES) &&
                     child &&
                     child->n_tasks_valid &&
                     streq(controller, SYSTEMD_CGROUP_CONTROLLER)) {
@@ -409,6 +435,9 @@ static int refresh(const char *root, Hashmap *a, Hashmap *b, unsigned iteration)
         r = refresh_one("blkio", root, a, b, iteration, 0, NULL);
         if (r < 0)
                 return r;
+        r = refresh_one("pids", root, a, b, iteration, 0, NULL);
+        if (r < 0)
+                return r;
 
         return 0;
 }
@@ -549,7 +578,7 @@ static void display(Hashmap *a) {
                 printf("%s%-*s%s %s%7s%s %s%s%s %s%8s%s %s%8s%s %s%8s%s\n\n",
                        arg_order == ORDER_PATH ? ON : "", path_columns, "Control Group",
                        arg_order == ORDER_PATH ? OFF : "",
-                       arg_order == ORDER_TASKS ? ON : "", "Tasks",
+                       arg_order == ORDER_TASKS ? ON : "", arg_count == COUNT_PIDS ? "Tasks" : arg_count == COUNT_USERSPACE_PROCESSES ? "Procs" : "Proc+",
                        arg_order == ORDER_TASKS ? OFF : "",
                        arg_order == ORDER_CPU ? ON : "", buffer,
                        arg_order == ORDER_CPU ? OFF : "",
@@ -576,7 +605,7 @@ static void display(Hashmap *a) {
                 printf("%-*s", path_columns, ellipsized ?: path);
 
                 if (g->n_tasks_valid)
-                        printf(" %7u", g->n_tasks);
+                        printf(" %7" PRIu64, g->n_tasks);
                 else
                         fputs("       -", stdout);
 
@@ -602,15 +631,16 @@ static void help(void) {
                "  -h --help           Show this help\n"
                "     --version        Show package version\n"
                "  -p --order=path     Order by path\n"
-               "  -t --order=tasks    Order by number of tasks\n"
+               "  -t --order=tasks    Order by number of tasks/processes\n"
                "  -c --order=cpu      Order by CPU load (default)\n"
                "  -m --order=memory   Order by memory load\n"
                "  -i --order=io       Order by IO load\n"
                "  -r --raw            Provide raw (not human-readable) numbers\n"
                "     --cpu=percentage Show CPU usage as percentage (default)\n"
                "     --cpu=time       Show CPU usage as time\n"
-               "  -k                  Include kernel threads in task count\n"
-               "     --recursive=BOOL Sum up task count recursively\n"
+               "  -P                  Count userspace processes instead of tasks (excl. kernel)\n"
+               "  -k                  Count all processes instead of tasks (incl. kernel)\n"
+               "     --recursive=BOOL Sum up process count recursively\n"
                "  -d --delay=DELAY    Delay between updates\n"
                "  -n --iterations=N   Run for N iterations before exiting\n"
                "  -b --batch          Run in batch mode, accepting no input\n"
@@ -642,12 +672,13 @@ static int parse_argv(int argc, char *argv[]) {
                 {}
         };
 
+        bool recursive_unset = false;
         int c, r;
 
         assert(argc >= 1);
         assert(argv);
 
-        while ((c = getopt_long(argc, argv, "hptcmin:brd:k", options, NULL)) >= 0)
+        while ((c = getopt_long(argc, argv, "hptcmin:brd:kP", options, NULL)) >= 0)
 
                 switch (c) {
 
@@ -748,7 +779,11 @@ static int parse_argv(int argc, char *argv[]) {
                         break;
 
                 case 'k':
-                        arg_kernel_threads = true;
+                        arg_count = COUNT_ALL_PROCESSES;
+                        break;
+
+                case 'P':
+                        arg_count = COUNT_USERSPACE_PROCESSES;
                         break;
 
                 case ARG_RECURSIVE:
@@ -759,6 +794,7 @@ static int parse_argv(int argc, char *argv[]) {
                         }
 
                         arg_recursive = r;
+                        recursive_unset = r == 0;
                         break;
 
                 case '?':
@@ -773,9 +809,23 @@ static int parse_argv(int argc, char *argv[]) {
                 return -EINVAL;
         }
 
+        if (recursive_unset && arg_count == COUNT_PIDS) {
+                log_error("Non-recursive counting is only supported when counting processes, not tasks. Use -P or -k.");
+                return -EINVAL;
+        }
+
         return 1;
 }
 
+static const char* counting_what(void) {
+        if (arg_count == COUNT_PIDS)
+                return "tasks";
+        else if (arg_count == COUNT_ALL_PROCESSES)
+                return "all processes (incl. kernel)";
+        else
+                return "userspace processes (excl. kernel)";
+}
+
 int main(int argc, char *argv[]) {
         int r;
         Hashmap *a = NULL, *b = NULL;
@@ -783,10 +833,19 @@ int main(int argc, char *argv[]) {
         usec_t last_refresh = 0;
         bool quit = false, immediate_refresh = false;
         _cleanup_free_ char *root = NULL;
+        CGroupMask mask;
 
         log_parse_environment();
         log_open();
 
+        r = cg_mask_supported(&mask);
+        if (r < 0) {
+                log_error_errno(r, "Failed to determine supported controllers: %m");
+                goto finish;
+        }
+
+        arg_count = (mask & CGROUP_MASK_PIDS) ? COUNT_PIDS : COUNT_USERSPACE_PROCESSES;
+
         r = parse_argv(argc, argv);
         if (r <= 0)
                 goto finish;
@@ -899,15 +958,26 @@ int main(int argc, char *argv[]) {
                         break;
 
                 case 'k':
-                        arg_kernel_threads = !arg_kernel_threads;
-                        fprintf(stdout, "\nCounting kernel threads: %s.", yes_no(arg_kernel_threads));
+                        arg_count = arg_count != COUNT_ALL_PROCESSES ? COUNT_ALL_PROCESSES : COUNT_PIDS;
+                        fprintf(stdout, "\nCounting: %s.", counting_what());
+                        fflush(stdout);
+                        sleep(1);
+                        break;
+
+                case 'P':
+                        arg_count = arg_count != COUNT_USERSPACE_PROCESSES ? COUNT_USERSPACE_PROCESSES : COUNT_PIDS;
+                        fprintf(stdout, "\nCounting: %s.", counting_what());
                         fflush(stdout);
                         sleep(1);
                         break;
 
                 case 'r':
-                        arg_recursive = !arg_recursive;
-                        fprintf(stdout, "\nRecursive task counting: %s", yes_no(arg_recursive));
+                        if (arg_count == COUNT_PIDS)
+                                fprintf(stdout, "\n\aCannot toggle recursive counting, not available in task counting mode.");
+                        else {
+                                arg_recursive = !arg_recursive;
+                                fprintf(stdout, "\nRecursive process counting: %s", yes_no(arg_recursive));
+                        }
                         fflush(stdout);
                         sleep(1);
                         break;
@@ -939,9 +1009,10 @@ int main(int argc, char *argv[]) {
                 case '?':
                 case 'h':
                         fprintf(stdout,
-                                "\t<" ON "p" OFF "> By path; <" ON "t" OFF "> By tasks; <" ON "c" OFF "> By CPU; <" ON "m" OFF "> By memory; <" ON "i" OFF "> By I/O\n"
+                                "\t<" ON "p" OFF "> By path; <" ON "t" OFF "> By tasks/procs; <" ON "c" OFF "> By CPU; <" ON "m" OFF "> By memory; <" ON "i" OFF "> By I/O\n"
                                 "\t<" ON "+" OFF "> Inc. delay; <" ON "-" OFF "> Dec. delay; <" ON "%%" OFF "> Toggle time; <" ON "SPACE" OFF "> Refresh\n"
-                                "\t<" ON "k" OFF "> Count kernel threads; <" ON "r" OFF "> Count recursively; <" ON "q" OFF "> Quit");
+                                "\t<" ON "P" OFF "> Toggle count userspace processes; <" ON "k" OFF "> Toggle count all processes\n"
+                                "\t<" ON "r" OFF "> Count processes recursively; <" ON "q" OFF "> Quit");
                         fflush(stdout);
                         sleep(3);
                         break;
diff --git a/src/core/cgroup.c b/src/core/cgroup.c
index baa7cc5488..48000d4e6e 100644
--- a/src/core/cgroup.c
+++ b/src/core/cgroup.c
@@ -22,10 +22,11 @@
 #include <fcntl.h>
 #include <fnmatch.h>
 
-#include "process-util.h"
+#include "cgroup-util.h"
 #include "path-util.h"
+#include "process-util.h"
 #include "special.h"
-#include "cgroup-util.h"
+
 #include "cgroup.h"
 
 #define CGROUP_CPU_QUOTA_PERIOD_USEC ((usec_t) 100 * USEC_PER_MSEC)
@@ -41,6 +42,7 @@ void cgroup_context_init(CGroupContext *c) {
         c->memory_limit = (uint64_t) -1;
         c->blockio_weight = (unsigned long) -1;
         c->startup_blockio_weight = (unsigned long) -1;
+        c->tasks_max = (uint64_t) -1;
 
         c->cpu_quota_per_sec_usec = USEC_INFINITY;
 }
@@ -106,6 +108,7 @@ void cgroup_context_dump(CGroupContext *c, FILE* f, const char *prefix) {
                 "%sBlockIOWeight=%lu\n"
                 "%sStartupBlockIOWeight=%lu\n"
                 "%sMemoryLimit=%" PRIu64 "\n"
+                "%sTasksMax=%" PRIu64 "\n"
                 "%sDevicePolicy=%s\n"
                 "%sDelegate=%s\n",
                 prefix, yes_no(c->cpu_accounting),
@@ -117,6 +120,7 @@ void cgroup_context_dump(CGroupContext *c, FILE* f, const char *prefix) {
                 prefix, c->blockio_weight,
                 prefix, c->startup_blockio_weight,
                 prefix, c->memory_limit,
+                prefix, c->tasks_max,
                 prefix, cgroup_device_policy_to_string(c->device_policy),
                 prefix, yes_no(c->delegate));
 
@@ -466,6 +470,21 @@ void cgroup_context_apply(CGroupContext *c, CGroupMask mask, const char *path, M
                                 log_debug("Ignoring device %s while writing cgroup attribute.", a->path);
                 }
         }
+
+        if ((mask & CGROUP_MASK_PIDS) && !is_root) {
+
+                if (c->tasks_max != (uint64_t) -1) {
+                        char buf[DECIMAL_STR_MAX(uint64_t) + 2];
+
+                        sprintf(buf, "%" PRIu64 "\n", c->tasks_max);
+                        r = cg_set_attribute("pids", path, "pids.max", buf);
+                } else
+                        r = cg_set_attribute("pids", path, "pids.max", "max");
+
+                if (r < 0)
+                        log_full_errno(IN_SET(r, -ENOENT, -EROFS) ? LOG_DEBUG : LOG_WARNING, r,
+                                       "Failed to set pids.max on %s: %m", path);
+        }
 }
 
 CGroupMask cgroup_context_get_mask(CGroupContext *c) {
@@ -494,6 +513,10 @@ CGroupMask cgroup_context_get_mask(CGroupContext *c) {
             c->device_policy != CGROUP_AUTO)
                 mask |= CGROUP_MASK_DEVICES;
 
+        if (c->tasks_accounting ||
+            c->tasks_max != (uint64_t) -1)
+                mask |= CGROUP_MASK_PIDS;
+
         return mask;
 }
 
@@ -1459,6 +1482,28 @@ int unit_get_memory_current(Unit *u, uint64_t *ret) {
         return safe_atou64(v, ret);
 }
 
+int unit_get_tasks_current(Unit *u, uint64_t *ret) {
+        _cleanup_free_ char *v = NULL;
+        int r;
+
+        assert(u);
+        assert(ret);
+
+        if (!u->cgroup_path)
+                return -ENODATA;
+
+        if ((u->cgroup_realized_mask & CGROUP_MASK_PIDS) == 0)
+                return -ENODATA;
+
+        r = cg_get_attribute("pids", u->cgroup_path, "pids.current", &v);
+        if (r == -ENOENT)
+                return -ENODATA;
+        if (r < 0)
+                return r;
+
+        return safe_atou64(v, ret);
+}
+
 static int unit_get_cpu_usage_raw(Unit *u, nsec_t *ret) {
         _cleanup_free_ char *v = NULL;
         uint64_t ns;
diff --git a/src/core/cgroup.h b/src/core/cgroup.h
index 438f5bf50f..3ba09d56a4 100644
--- a/src/core/cgroup.h
+++ b/src/core/cgroup.h
@@ -72,6 +72,7 @@ struct CGroupContext {
         bool cpu_accounting;
         bool blockio_accounting;
         bool memory_accounting;
+        bool tasks_accounting;
 
         unsigned long cpu_shares;
         unsigned long startup_cpu_shares;
@@ -88,6 +89,8 @@ struct CGroupContext {
         LIST_HEAD(CGroupDeviceAllow, device_allow);
 
         bool delegate;
+
+        uint64_t tasks_max;
 };
 
 #include "unit.h"
@@ -137,6 +140,7 @@ int unit_search_main_pid(Unit *u, pid_t *ret);
 int unit_watch_all_pids(Unit *u);
 
 int unit_get_memory_current(Unit *u, uint64_t *ret);
+int unit_get_tasks_current(Unit *u, uint64_t *ret);
 int unit_get_cpu_usage(Unit *u, nsec_t *ret);
 int unit_reset_cpu_usage(Unit *u);
 
diff --git a/src/core/dbus-cgroup.c b/src/core/dbus-cgroup.c
index ba2f4e53b9..94de92c3dd 100644
--- a/src/core/dbus-cgroup.c
+++ b/src/core/dbus-cgroup.c
@@ -168,6 +168,8 @@ const sd_bus_vtable bus_cgroup_vtable[] = {
         SD_BUS_PROPERTY("MemoryLimit", "t", NULL, offsetof(CGroupContext, memory_limit), 0),
         SD_BUS_PROPERTY("DevicePolicy", "s", property_get_cgroup_device_policy, offsetof(CGroupContext, device_policy), 0),
         SD_BUS_PROPERTY("DeviceAllow", "a(ss)", property_get_device_allow, 0, 0),
+        SD_BUS_PROPERTY("TasksAccounting", "b", bus_property_get_bool, offsetof(CGroupContext, tasks_accounting), 0),
+        SD_BUS_PROPERTY("TasksMax", "t", NULL, offsetof(CGroupContext, tasks_max), 0),
         SD_BUS_VTABLE_END
 };
 
@@ -551,7 +553,11 @@ int bus_cgroup_set_property(
                 if (mode != UNIT_CHECK) {
                         c->memory_limit = limit;
                         u->cgroup_realized_mask &= ~CGROUP_MASK_MEMORY;
-                        unit_write_drop_in_private_format(u, mode, name, "%s=%" PRIu64, name, limit);
+
+                        if (limit == (uint64_t) -1)
+                                unit_write_drop_in_private(u, mode, name, "MemoryLimit=infinity");
+                        else
+                                unit_write_drop_in_private_format(u, mode, name, "MemoryLimit=%" PRIu64, limit);
                 }
 
                 return 1;
@@ -667,6 +673,39 @@ int bus_cgroup_set_property(
 
                 return 1;
 
+        } else if (streq(name, "TasksAccounting")) {
+                int b;
+
+                r = sd_bus_message_read(message, "b", &b);
+                if (r < 0)
+                        return r;
+
+                if (mode != UNIT_CHECK) {
+                        c->tasks_accounting = b;
+                        u->cgroup_realized_mask &= ~CGROUP_MASK_PIDS;
+                        unit_write_drop_in_private(u, mode, name, b ? "TasksAccounting=yes" : "TasksAccounting=no");
+                }
+
+                return 1;
+
+        } else if (streq(name, "TasksMax")) {
+                uint64_t limit;
+
+                r = sd_bus_message_read(message, "t", &limit);
+                if (r < 0)
+                        return r;
+
+                if (mode != UNIT_CHECK) {
+                        c->tasks_max = limit;
+                        u->cgroup_realized_mask &= ~CGROUP_MASK_PIDS;
+
+                        if (limit == (uint64_t) -1)
+                                unit_write_drop_in_private(u, mode, name, "TasksMax=infinity");
+                        else
+                                unit_write_drop_in_private_format(u, mode, name, "TasksMax=%" PRIu64, limit);
+                }
+
+                return 1;
         }
 
         if (u->transient && u->load_state == UNIT_STUB) {
diff --git a/src/core/dbus-unit.c b/src/core/dbus-unit.c
index f9275ed935..f7e9795928 100644
--- a/src/core/dbus-unit.c
+++ b/src/core/dbus-unit.c
@@ -736,6 +736,30 @@ static int property_get_current_memory(
         return sd_bus_message_append(reply, "t", sz);
 }
 
+static int property_get_current_tasks(
+                sd_bus *bus,
+                const char *path,
+                const char *interface,
+                const char *property,
+                sd_bus_message *reply,
+                void *userdata,
+                sd_bus_error *error) {
+
+        uint64_t cn = (uint64_t) -1;
+        Unit *u = userdata;
+        int r;
+
+        assert(bus);
+        assert(reply);
+        assert(u);
+
+        r = unit_get_tasks_current(u, &cn);
+        if (r < 0 && r != -ENODATA)
+                log_unit_warning_errno(u, r, "Failed to get pids.current attribute: %m");
+
+        return sd_bus_message_append(reply, "t", cn);
+}
+
 static int property_get_cpu_usage(
                 sd_bus *bus,
                 const char *path,
@@ -796,6 +820,7 @@ const sd_bus_vtable bus_unit_cgroup_vtable[] = {
         SD_BUS_PROPERTY("ControlGroup", "s", property_get_cgroup, 0, 0),
         SD_BUS_PROPERTY("MemoryCurrent", "t", property_get_current_memory, 0, 0),
         SD_BUS_PROPERTY("CPUUsageNSec", "t", property_get_cpu_usage, 0, 0),
+        SD_BUS_PROPERTY("TasksCurrent", "t", property_get_current_tasks, 0, 0),
         SD_BUS_VTABLE_END
 };
 
diff --git a/src/core/load-fragment-gperf.gperf.m4 b/src/core/load-fragment-gperf.gperf.m4
index edd55b9e45..e056fd863c 100644
--- a/src/core/load-fragment-gperf.gperf.m4
+++ b/src/core/load-fragment-gperf.gperf.m4
@@ -124,6 +124,8 @@ $1.StartupBlockIOWeight,         config_parse_blockio_weight,        0,
 $1.BlockIODeviceWeight,          config_parse_blockio_device_weight, 0,                             offsetof($1, cgroup_context)
 $1.BlockIOReadBandwidth,         config_parse_blockio_bandwidth,     0,                             offsetof($1, cgroup_context)
 $1.BlockIOWriteBandwidth,        config_parse_blockio_bandwidth,     0,                             offsetof($1, cgroup_context)
+$1.TasksAccounting,              config_parse_bool,                  0,                             offsetof($1, cgroup_context.tasks_accounting)
+$1.TasksMax,                     config_parse_tasks_max,             0,                             offsetof($1, cgroup_context)
 $1.Delegate,                     config_parse_bool,                  0,                             offsetof($1, cgroup_context.delegate)'
 )m4_dnl
 Unit.Description,                config_parse_unit_string_printf,    0,                             offsetof(Unit, description)
diff --git a/src/core/load-fragment.c b/src/core/load-fragment.c
index 00cc6f7373..f7a8539910 100644
--- a/src/core/load-fragment.c
+++ b/src/core/load-fragment.c
@@ -2686,15 +2686,14 @@ int config_parse_memory_limit(
         uint64_t bytes;
         int r;
 
-        if (isempty(rvalue)) {
+        if (isempty(rvalue) || streq(rvalue, "infinity")) {
                 c->memory_limit = (uint64_t) -1;
                 return 0;
         }
 
         r = parse_size(rvalue, 1024, &bytes);
-        if (r < 0) {
-                log_syntax(unit, LOG_ERR, filename, line, EINVAL,
-                           "Memory limit '%s' invalid. Ignoring.", rvalue);
+        if (r < 0 || bytes < 1) {
+                log_syntax(unit, LOG_ERR, filename, line, EINVAL, "Memory limit '%s' invalid. Ignoring.", rvalue);
                 return 0;
         }
 
@@ -2702,6 +2701,36 @@ int config_parse_memory_limit(
         return 0;
 }
 
+int config_parse_tasks_max(
+                const char *unit,
+                const char *filename,
+                unsigned line,
+                const char *section,
+                unsigned section_line,
+                const char *lvalue,
+                int ltype,
+                const char *rvalue,
+                void *data,
+                void *userdata) {
+
+        CGroupContext *c = data;
+        uint64_t u;
+        int r;
+
+        if (isempty(rvalue) || streq(rvalue, "infinity")) {
+                c->tasks_max = (uint64_t) -1;
+                return 0;
+        }
+
+        r = safe_atou64(rvalue, &u);
+        if (r < 0 || u < 1) {
+                log_syntax(unit, LOG_ERR, filename, line, EINVAL, "Maximum tasks value '%s' invalid. Ignoring.", rvalue);
+                return 0;
+        }
+
+        return 0;
+}
+
 int config_parse_device_allow(
                 const char *unit,
                 const char *filename,
diff --git a/src/core/load-fragment.h b/src/core/load-fragment.h
index 1d128716c4..638b343a6e 100644
--- a/src/core/load-fragment.h
+++ b/src/core/load-fragment.h
@@ -84,6 +84,7 @@ int config_parse_environ(const char *unit, const char *filename, unsigned line,
 int config_parse_unit_slice(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
 int config_parse_cpu_shares(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
 int config_parse_memory_limit(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
+int config_parse_tasks_max(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
 int config_parse_device_policy(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
 int config_parse_device_allow(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
 int config_parse_blockio_weight(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
diff --git a/src/core/main.c b/src/core/main.c
index c9657505c3..200fe740da 100644
--- a/src/core/main.c
+++ b/src/core/main.c
@@ -114,6 +114,7 @@ static FILE* arg_serialization = NULL;
 static bool arg_default_cpu_accounting = false;
 static bool arg_default_blockio_accounting = false;
 static bool arg_default_memory_accounting = false;
+static bool arg_default_tasks_accounting = false;
 
 static void nop_handler(int sig) {}
 
@@ -676,6 +677,7 @@ static int parse_config_file(void) {
                 { "Manager", "DefaultCPUAccounting",      config_parse_bool,             0, &arg_default_cpu_accounting            },
                 { "Manager", "DefaultBlockIOAccounting",  config_parse_bool,             0, &arg_default_blockio_accounting        },
                 { "Manager", "DefaultMemoryAccounting",   config_parse_bool,             0, &arg_default_memory_accounting         },
+                { "Manager", "DefaultTasksAccounting",    config_parse_bool,             0, &arg_default_tasks_accounting          },
                 {}
         };
 
@@ -704,6 +706,7 @@ static void manager_set_defaults(Manager *m) {
         m->default_cpu_accounting = arg_default_cpu_accounting;
         m->default_blockio_accounting = arg_default_blockio_accounting;
         m->default_memory_accounting = arg_default_memory_accounting;
+        m->default_tasks_accounting = arg_default_tasks_accounting;
 
         manager_set_default_rlimits(m, arg_default_rlimit);
         manager_environment_add(m, NULL, arg_default_environment);
diff --git a/src/core/manager.h b/src/core/manager.h
index 9956cb7700..78a0e50a33 100644
--- a/src/core/manager.h
+++ b/src/core/manager.h
@@ -256,6 +256,7 @@ struct Manager {
         bool default_cpu_accounting;
         bool default_memory_accounting;
         bool default_blockio_accounting;
+        bool default_tasks_accounting;
 
         usec_t default_timer_accuracy_usec;
 
diff --git a/src/core/unit.c b/src/core/unit.c
index e40ea24be8..2ebfb09a7a 100644
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -125,6 +125,7 @@ static void unit_init(Unit *u) {
                 cc->cpu_accounting = u->manager->default_cpu_accounting;
                 cc->blockio_accounting = u->manager->default_blockio_accounting;
                 cc->memory_accounting = u->manager->default_memory_accounting;
+                cc->tasks_accounting = u->manager->default_tasks_accounting;
         }
 
         ec = unit_get_exec_context(u);
diff --git a/src/shared/bus-util.c b/src/shared/bus-util.c
index 64a810fc8f..4dc4ca581d 100644
--- a/src/shared/bus-util.c
+++ b/src/shared/bus-util.c
@@ -1421,7 +1421,7 @@ int bus_append_unit_property_assignment(sd_bus_message *m, const char *assignmen
                 return bus_log_create_error(r);
 
         if (STR_IN_SET(field,
-                       "CPUAccounting", "MemoryAccounting", "BlockIOAccounting",
+                       "CPUAccounting", "MemoryAccounting", "BlockIOAccounting", "TasksAccounting",
                        "SendSIGHUP", "SendSIGKILL", "WakeSystem", "DefaultDependencies",
                        "IgnoreSIGPIPE", "TTYVHangup", "TTYReset", "RemainAfterExit")) {
 
@@ -1436,14 +1436,33 @@ int bus_append_unit_property_assignment(sd_bus_message *m, const char *assignmen
         } else if (streq(field, "MemoryLimit")) {
                 uint64_t bytes;
 
-                r = parse_size(eq, 1024, &bytes);
-                if (r < 0) {
-                        log_error("Failed to parse bytes specification %s", assignment);
-                        return -EINVAL;
+                if (isempty(eq) || streq(eq, "infinity"))
+                        bytes = (uint64_t) -1;
+                else {
+                        r = parse_size(eq, 1024, &bytes);
+                        if (r < 0) {
+                                log_error("Failed to parse bytes specification %s", assignment);
+                                return -EINVAL;
+                        }
                 }
 
                 r = sd_bus_message_append(m, "v", "t", bytes);
 
+        } else if (streq(field, "TasksMax")) {
+                uint64_t n;
+
+                if (isempty(eq) || streq(eq, "infinity"))
+                        n = (uint64_t) -1;
+                else {
+                        r = safe_atou64(eq, &n);
+                        if (r < 0) {
+                                log_error("Failed to parse maximum tasks specification %s", assignment);
+                                return -EINVAL;
+                        }
+                }
+
+                r = sd_bus_message_append(m, "v", "t", n);
+
         } else if (STR_IN_SET(field, "CPUShares", "BlockIOWeight")) {
                 uint64_t u;
 
diff --git a/src/systemctl/systemctl.c b/src/systemctl/systemctl.c
index 5aa4e07d57..e265d0fd13 100644
--- a/src/systemctl/systemctl.c
+++ b/src/systemctl/systemctl.c
@@ -20,59 +20,60 @@
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#include <sys/reboot.h>
-#include <linux/reboot.h>
-#include <stdio.h>
+#include <errno.h>
+#include <fcntl.h>
 #include <getopt.h>
+#include <linux/reboot.h>
 #include <locale.h>
 #include <stdbool.h>
+#include <stddef.h>
+#include <stdio.h>
 #include <string.h>
-#include <errno.h>
-#include <unistd.h>
-#include <fcntl.h>
+#include <sys/reboot.h>
 #include <sys/socket.h>
-#include <stddef.h>
+#include <unistd.h>
 
+#include "sd-bus.h"
 #include "sd-daemon.h"
 #include "sd-login.h"
-#include "sd-bus.h"
-#include "log.h"
-#include "util.h"
-#include "macro.h"
-#include "set.h"
-#include "utmp-wtmp.h"
-#include "special.h"
-#include "initreq.h"
-#include "path-util.h"
-#include "strv.h"
+
+#include "build.h"
+#include "bus-common-errors.h"
+#include "bus-error.h"
+#include "bus-message.h"
+#include "bus-util.h"
 #include "cgroup-show.h"
 #include "cgroup-util.h"
-#include "list.h"
-#include "path-lookup.h"
-#include "exit-status.h"
-#include "build.h"
-#include "unit-name.h"
-#include "pager.h"
-#include "spawn-ask-password-agent.h"
-#include "spawn-polkit-agent.h"
-#include "install.h"
-#include "logs-show.h"
-#include "socket-util.h"
-#include "fileio.h"
 #include "copy.h"
-#include "env-util.h"
-#include "bus-util.h"
-#include "bus-message.h"
-#include "bus-error.h"
-#include "bus-common-errors.h"
-#include "mkdir.h"
 #include "dropin.h"
 #include "efivars.h"
+#include "env-util.h"
+#include "exit-status.h"
+#include "fileio.h"
 #include "formats-util.h"
-#include "process-util.h"
-#include "terminal-util.h"
 #include "hostname-util.h"
+#include "initreq.h"
+#include "install.h"
+#include "list.h"
+#include "log.h"
+#include "logs-show.h"
+#include "macro.h"
+#include "mkdir.h"
+#include "pager.h"
+#include "path-lookup.h"
+#include "path-util.h"
+#include "process-util.h"
+#include "set.h"
 #include "signal-util.h"
+#include "socket-util.h"
+#include "spawn-ask-password-agent.h"
+#include "spawn-polkit-agent.h"
+#include "special.h"
+#include "strv.h"
+#include "terminal-util.h"
+#include "unit-name.h"
+#include "util.h"
+#include "utmp-wtmp.h"
 
 static char **arg_types = NULL;
 static char **arg_states = NULL;
@@ -3285,6 +3286,8 @@ typedef struct UnitStatusInfo {
         uint64_t memory_current;
         uint64_t memory_limit;
         uint64_t cpu_usage_nsec;
+        uint64_t tasks_current;
+        uint64_t tasks_max;
 
         LIST_HEAD(ExecStatusInfo, exec);
 } UnitStatusInfo;
@@ -3543,6 +3546,15 @@ static void print_status_info(
         if (i->status_errno > 0)
                 printf("    Error: %i (%s)\n", i->status_errno, strerror(i->status_errno));
 
+        if (i->tasks_current != (uint64_t) -1) {
+                printf("    Tasks: %" PRIu64, i->tasks_current);
+
+                if (i->tasks_max != (uint64_t) -1)
+                        printf(" (limit: %" PRIi64 ")\n", i->tasks_max);
+                else
+                        printf("\n");
+        }
+
         if (i->memory_current != (uint64_t) -1) {
                 char buf[FORMAT_BYTES_MAX];
 
@@ -3776,6 +3788,10 @@ static int status_property(const char *name, sd_bus_message *m, UnitStatusInfo *
                         i->memory_current = u;
                 else if (streq(name, "MemoryLimit"))
                         i->memory_limit = u;
+                else if (streq(name, "TasksCurrent"))
+                        i->tasks_current = u;
+                else if (streq(name, "TasksMax"))
+                        i->tasks_max = u;
                 else if (streq(name, "CPUUsageNSec"))
                         i->cpu_usage_nsec = u;
 
@@ -4252,6 +4268,8 @@ static int show_one(
                 .memory_current = (uint64_t) -1,
                 .memory_limit = (uint64_t) -1,
                 .cpu_usage_nsec = (uint64_t) -1,
+                .tasks_current = (uint64_t) -1,
+                .tasks_max = (uint64_t) -1,
         };
         ExecStatusInfo *p;
         int r;