add support for KSM

This adds support for KSM (kernel samepage merging). It adds a new
boolean parameter called MemoryKSM to enable the feature. The feature
can only be enabled with newer kernels.

src/shared/bus-unit-util.c

@@ -991,6 +991,7 @@ static int bus_append_execute_property(sd_bus_message *m, const char *field, con
                               "CPUSchedulingResetOnFork",
                               "LockPersonality",
                               "ProtectHostname",
+                              "MemoryKSM",
                               "RestrictSUIDSGID"))
                 return bus_append_parse_boolean(m, field, eq);
 

src/shared/exit-status.c

@@ -72,6 +72,7 @@ const ExitStatusMapping exit_status_mappings[256] = {
         [EXIT_NUMA_POLICY] =             { "NUMA_POLICY",             EXIT_STATUS_SYSTEMD },
         [EXIT_CREDENTIALS] =             { "CREDENTIALS",             EXIT_STATUS_SYSTEMD },
         [EXIT_BPF] =                     { "BPF",                     EXIT_STATUS_SYSTEMD },
+        [EXIT_KSM] =                     { "KSM",                     EXIT_STATUS_SYSTEMD },
 
         [EXIT_EXCEPTION] =               { "EXCEPTION",               EXIT_STATUS_SYSTEMD },
 

src/shared/exit-status.h

@@ -72,6 +72,7 @@ enum {
         EXIT_NUMA_POLICY,
         EXIT_CREDENTIALS,
         EXIT_BPF,
+        EXIT_KSM,
 
         EXIT_EXCEPTION = 255,  /* Whenever we want to propagate an abnormal/signal exit, in line with bash */
 };