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, 28 insertions, 0 deletions

diff --git a/src/core/dbus-cgroup.c b/src/core/dbus-cgroup.c
index d6053581f8..27050b4507 100644
--- a/src/core/dbus-cgroup.c
+++ b/src/core/dbus-cgroup.c
@@ -228,6 +228,9 @@ const sd_bus_vtable bus_cgroup_vtable[] = {
         SD_BUS_PROPERTY("BlockIOReadBandwidth", "a(st)", property_get_blockio_device_bandwidths, 0, 0),
         SD_BUS_PROPERTY("BlockIOWriteBandwidth", "a(st)", property_get_blockio_device_bandwidths, 0, 0),
         SD_BUS_PROPERTY("MemoryAccounting", "b", bus_property_get_bool, offsetof(CGroupContext, memory_accounting), 0),
+        SD_BUS_PROPERTY("MemoryLow", "t", NULL, offsetof(CGroupContext, memory_low), 0),
+        SD_BUS_PROPERTY("MemoryHigh", "t", NULL, offsetof(CGroupContext, memory_high), 0),
+        SD_BUS_PROPERTY("MemoryMax", "t", NULL, offsetof(CGroupContext, memory_max), 0),
         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),
@@ -826,6 +829,31 @@ int bus_cgroup_set_property(
 
                 return 1;
 
+        } else if (STR_IN_SET(name, "MemoryLow", "MemoryHigh", "MemoryMax")) {
+                uint64_t v;
+
+                r = sd_bus_message_read(message, "t", &v);
+                if (r < 0)
+                        return r;
+
+                if (mode != UNIT_CHECK) {
+                        if (streq(name, "MemoryLow"))
+                                c->memory_low = v;
+                        else if (streq(name, "MemoryHigh"))
+                                c->memory_high = v;
+                        else
+                                c->memory_max = v;
+
+                        unit_invalidate_cgroup(u, CGROUP_MASK_MEMORY);
+
+                        if (v == CGROUP_LIMIT_MAX)
+                                unit_write_drop_in_private_format(u, mode, name, "%s=max\n", name);
+                        else
+                                unit_write_drop_in_private_format(u, mode, name, "%s=%" PRIu64 "\n", name, v);
+                }
+
+                return 1;
+
         } else if (streq(name, "MemoryLimit")) {
                 uint64_t limit;