core: add cgroup memory controller support on the unified hierarchy (#3315)

On the unified hierarchy, memory controller implements three control knobs -
low, high and max which enables more useable and versatile control over memory
usage.  This patch implements support for the three control knobs.

* MemoryLow, MemoryHigh and MemoryMax are added for memory.low, memory.high and
  memory.max, respectively.

* As all absolute limits on the unified hierarchy use "max" for no limit, make
  memory limit parse functions accept "max" in addition to "infinity" and
  document "max" for the new knobs.

* Implement compatibility translation between MemoryMax and MemoryLimit.

v2:

- Fixed missing else's in config_parse_memory_limit().
- Fixed missing newline when writing out drop-ins.
- Coding style updates to use "val > 0" instead of "val".
- Minor updates to documentation.

1 files changed, 35 insertions, 4 deletions

diff --git a/src/systemctl/systemctl.c b/src/systemctl/systemctl.c
index 0500593d06..b2ee00fab3 100644
--- a/src/systemctl/systemctl.c
+++ b/src/systemctl/systemctl.c
@@ -3493,6 +3493,9 @@ typedef struct UnitStatusInfo {
 
         /* CGroup */
         uint64_t memory_current;
+        uint64_t memory_low;
+        uint64_t memory_high;
+        uint64_t memory_max;
         uint64_t memory_limit;
         uint64_t cpu_usage_nsec;
         uint64_t tasks_current;
@@ -3775,10 +3778,30 @@ static void print_status_info(
 
                 printf("   Memory: %s", format_bytes(buf, sizeof(buf), i->memory_current));
 
-                if (i->memory_limit != (uint64_t) -1)
-                        printf(" (limit: %s)\n", format_bytes(buf, sizeof(buf), i->memory_limit));
-                else
-                        printf("\n");
+                if (i->memory_low > 0 || i->memory_high != CGROUP_LIMIT_MAX || i->memory_max != CGROUP_LIMIT_MAX ||
+                    i->memory_limit != CGROUP_LIMIT_MAX) {
+                        const char *prefix = "";
+
+                        printf(" (");
+                        if (i->memory_low > 0) {
+                                printf("%slow: %s", prefix, format_bytes(buf, sizeof(buf), i->memory_low));
+                                prefix = " ";
+                        }
+                        if (i->memory_high != CGROUP_LIMIT_MAX) {
+                                printf("%shigh: %s", prefix, format_bytes(buf, sizeof(buf), i->memory_high));
+                                prefix = " ";
+                        }
+                        if (i->memory_max != CGROUP_LIMIT_MAX) {
+                                printf("%smax: %s", prefix, format_bytes(buf, sizeof(buf), i->memory_max));
+                                prefix = " ";
+                        }
+                        if (i->memory_limit != CGROUP_LIMIT_MAX) {
+                                printf("%slimit: %s", prefix, format_bytes(buf, sizeof(buf), i->memory_limit));
+                                prefix = " ";
+                        }
+                        printf(")");
+                }
+                printf("\n");
         }
 
         if (i->cpu_usage_nsec != (uint64_t) -1) {
@@ -4007,6 +4030,12 @@ static int status_property(const char *name, sd_bus_message *m, UnitStatusInfo *
                         i->assert_timestamp = (usec_t) u;
                 else if (streq(name, "MemoryCurrent"))
                         i->memory_current = u;
+                else if (streq(name, "MemoryLow"))
+                        i->memory_low = u;
+                else if (streq(name, "MemoryHigh"))
+                        i->memory_high = u;
+                else if (streq(name, "MemoryMax"))
+                        i->memory_max = u;
                 else if (streq(name, "MemoryLimit"))
                         i->memory_limit = u;
                 else if (streq(name, "TasksCurrent"))
@@ -4500,6 +4529,8 @@ static int show_one(
         _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
         UnitStatusInfo info = {
                 .memory_current = (uint64_t) -1,
+                .memory_high = CGROUP_LIMIT_MAX,
+                .memory_max = CGROUP_LIMIT_MAX,
                 .memory_limit = (uint64_t) -1,
                 .cpu_usage_nsec = (uint64_t) -1,
                 .tasks_current = (uint64_t) -1,