From: Michal Schmidt <mschmidt@redhat.com>
Date: Sun, 15 Jan 2012 09:53:49 +0000 (+0100)
Subject: unit: reduce heap usage for unit objects
X-Git-Tag: v39~48
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=7d17cfbc46306a106dbda0f3e92fbc0792d1e9e9;p=thirdparty%2Fsystemd.git

unit: reduce heap usage for unit objects

The storage of the unit objects on the heap is currently not very
efficient. For every unit object we allocate a chunk of memory as large
as the biggest unit type, although there are significant differences in
the units' real requirements.
pahole shows the following sizes of structs:
488  Target
496  Snapshot
512  Device
528  Path
560  Timer
576  Automount
1080 Socket
1160 Swap
1168 Service
1280 Mount

Usually there aren't many targets or snapshots in the system, but Device
is one of the most common unit types and for every one we waste
1280 - 512 = 768 bytes.

Fix it by allocating only the right amount for the given unit type.
On my machine (x86_64, with 39 LVM volumes) this decreases systemd's
USS (unique set size) by more than 300 KB.
---

diff --git a/src/automount.c b/src/automount.c
index b70f8b4684a..c4191f6706e 100644
--- a/src/automount.c
+++ b/src/automount.c
@@ -836,6 +836,7 @@ DEFINE_STRING_TABLE_LOOKUP(automount_state, AutomountState);
 
 const UnitVTable automount_vtable = {
         .suffix = ".automount",
+        .object_size = sizeof(Automount),
         .sections =
                 "Unit\0"
                 "Automount\0"
diff --git a/src/device.c b/src/device.c
index bffeca0d10c..64665a8b87a 100644
--- a/src/device.c
+++ b/src/device.c
@@ -198,10 +198,12 @@ static int device_update_unit(Manager *m, struct udev_device *dev, const char *p
         if (!u) {
                 delete = true;
 
-                if (!(u = unit_new(m)))
+                u = unit_new(m, sizeof(Device));
+                if (!u)
                         return -ENOMEM;
 
-                if ((r = device_add_escaped_name(u, path)) < 0)
+                r = device_add_escaped_name(u, path);
+                if (r < 0)
                         goto fail;
 
                 unit_add_to_load_queue(u);
@@ -583,6 +585,7 @@ DEFINE_STRING_TABLE_LOOKUP(device_state, DeviceState);
 
 const UnitVTable device_vtable = {
         .suffix = ".device",
+        .object_size = sizeof(Device),
         .sections =
                 "Unit\0"
                 "Device\0"
diff --git a/src/manager.c b/src/manager.c
index a549209ca64..683197396f5 100644
--- a/src/manager.c
+++ b/src/manager.c
@@ -1795,6 +1795,7 @@ unsigned manager_dispatch_load_queue(Manager *m) {
 
 int manager_load_unit_prepare(Manager *m, const char *name, const char *path, DBusError *e, Unit **_ret) {
         Unit *ret;
+        UnitType t;
         int r;
 
         assert(m);
@@ -1811,24 +1812,30 @@ int manager_load_unit_prepare(Manager *m, const char *name, const char *path, DB
         if (!name)
                 name = file_name_from_path(path);
 
-        if (!unit_name_is_valid(name, false)) {
+        t = unit_name_to_type(name);
+
+        if (t == _UNIT_TYPE_INVALID || !unit_name_is_valid_no_type(name, false)) {
                 dbus_set_error(e, BUS_ERROR_INVALID_NAME, "Unit name %s is not valid.", name);
                 return -EINVAL;
         }
 
-        if ((ret = manager_get_unit(m, name))) {
+        ret = manager_get_unit(m, name);
+        if (ret) {
                 *_ret = ret;
                 return 1;
         }
 
-        if (!(ret = unit_new(m)))
+        ret = unit_new(m, unit_vtable[t]->object_size);
+        if (!ret)
                 return -ENOMEM;
 
-        if (path)
-                if (!(ret->meta.fragment_path = strdup(path))) {
+        if (path) {
+                ret->meta.fragment_path = strdup(path);
+                if (!ret->meta.fragment_path) {
                         unit_free(ret);
                         return -ENOMEM;
                 }
+        }
 
         if ((r = unit_add_name(ret, name)) < 0) {
                 unit_free(ret);
diff --git a/src/mount.c b/src/mount.c
index 12c0710f1fb..f94c0eb278d 100644
--- a/src/mount.c
+++ b/src/mount.c
@@ -1395,13 +1395,16 @@ static int mount_add_one(
         if (!is_path(where))
                 return 0;
 
-        if (!(e = unit_name_from_path(where, ".mount")))
+        e = unit_name_from_path(where, ".mount");
+        if (!e)
                 return -ENOMEM;
 
-        if (!(u = manager_get_unit(m, e))) {
+        u = manager_get_unit(m, e);
+        if (!u) {
                 delete = true;
 
-                if (!(u = unit_new(m))) {
+                u = unit_new(m, sizeof(Mount));
+                if (!u) {
                         free(e);
                         return -ENOMEM;
                 }
@@ -1412,7 +1415,8 @@ static int mount_add_one(
                 if (r < 0)
                         goto fail;
 
-                if (!(MOUNT(u)->where = strdup(where))) {
+                MOUNT(u)->where = strdup(where);
+                if (!MOUNT(u)->where) {
                         r = -ENOMEM;
                         goto fail;
                 }
@@ -1837,6 +1841,7 @@ DEFINE_STRING_TABLE_LOOKUP(mount_exec_command, MountExecCommand);
 
 const UnitVTable mount_vtable = {
         .suffix = ".mount",
+        .object_size = sizeof(Mount),
         .sections =
                 "Unit\0"
                 "Mount\0"
diff --git a/src/path.c b/src/path.c
index 957af05c7eb..ae5052aeab6 100644
--- a/src/path.c
+++ b/src/path.c
@@ -717,6 +717,7 @@ DEFINE_STRING_TABLE_LOOKUP(path_type, PathType);
 
 const UnitVTable path_vtable = {
         .suffix = ".path",
+        .object_size = sizeof(Path),
         .sections =
                 "Unit\0"
                 "Path\0"
diff --git a/src/service.c b/src/service.c
index 113be34ad0b..6ce6b19db9a 100644
--- a/src/service.c
+++ b/src/service.c
@@ -3553,6 +3553,7 @@ DEFINE_STRING_TABLE_LOOKUP(notify_access, NotifyAccess);
 
 const UnitVTable service_vtable = {
         .suffix = ".service",
+        .object_size = sizeof(Service),
         .sections =
                 "Unit\0"
                 "Service\0"
diff --git a/src/snapshot.c b/src/snapshot.c
index 270dc4f2525..161629d9839 100644
--- a/src/snapshot.c
+++ b/src/snapshot.c
@@ -282,6 +282,7 @@ DEFINE_STRING_TABLE_LOOKUP(snapshot_state, SnapshotState);
 
 const UnitVTable snapshot_vtable = {
         .suffix = ".snapshot",
+        .object_size = sizeof(Snapshot),
 
         .no_alias = true,
         .no_instances = true,
diff --git a/src/socket.c b/src/socket.c
index 7034436be06..1a245aa872e 100644
--- a/src/socket.c
+++ b/src/socket.c
@@ -2114,6 +2114,7 @@ DEFINE_STRING_TABLE_LOOKUP(socket_exec_command, SocketExecCommand);
 
 const UnitVTable socket_vtable = {
         .suffix = ".socket",
+        .object_size = sizeof(Socket),
         .sections =
                 "Unit\0"
                 "Socket\0"
diff --git a/src/swap.c b/src/swap.c
index 4fa30a3e325..202c4e6625f 100644
--- a/src/swap.c
+++ b/src/swap.c
@@ -334,7 +334,8 @@ int swap_add_one(
         assert(m);
         assert(what);
 
-        if (!(e = unit_name_from_path(what, ".swap")))
+        e = unit_name_from_path(what, ".swap");
+        if (!e)
                 return -ENOMEM;
 
         u = manager_get_unit(m, e);
@@ -348,15 +349,18 @@ int swap_add_one(
         if (!u) {
                 delete = true;
 
-                if (!(u = unit_new(m))) {
+                u = unit_new(m, sizeof(Swap));
+                if (!u) {
                         free(e);
                         return -ENOMEM;
                 }
 
-                if ((r = unit_add_name(u, e)) < 0)
+                r = unit_add_name(u, e);
+                if (r < 0)
                         goto fail;
 
-                if (!(SWAP(u)->what = strdup(what))) {
+                SWAP(u)->what = strdup(what);
+                if (!SWAP(u)->what) {
                         r = -ENOMEM;
                         goto fail;
                 }
@@ -1341,6 +1345,7 @@ DEFINE_STRING_TABLE_LOOKUP(swap_exec_command, SwapExecCommand);
 
 const UnitVTable swap_vtable = {
         .suffix = ".swap",
+        .object_size = sizeof(Swap),
         .sections =
                 "Unit\0"
                 "Swap\0"
diff --git a/src/target.c b/src/target.c
index 340e9907f0d..b774cfbc334 100644
--- a/src/target.c
+++ b/src/target.c
@@ -199,6 +199,7 @@ DEFINE_STRING_TABLE_LOOKUP(target_state, TargetState);
 
 const UnitVTable target_vtable = {
         .suffix = ".target",
+        .object_size = sizeof(Target),
         .sections =
                 "Unit\0"
                 "Target\0"
diff --git a/src/timer.c b/src/timer.c
index d127a117434..87adb29e7ae 100644
--- a/src/timer.c
+++ b/src/timer.c
@@ -468,6 +468,7 @@ DEFINE_STRING_TABLE_LOOKUP(timer_base, TimerBase);
 
 const UnitVTable timer_vtable = {
         .suffix = ".timer",
+        .object_size = sizeof(Timer),
         .sections =
                 "Unit\0"
                 "Timer\0"
diff --git a/src/unit.c b/src/unit.c
index 1fbfb1dea5f..fa3c2649b35 100644
--- a/src/unit.c
+++ b/src/unit.c
@@ -57,15 +57,18 @@ const UnitVTable * const unit_vtable[_UNIT_TYPE_MAX] = {
         [UNIT_PATH] = &path_vtable
 };
 
-Unit *unit_new(Manager *m) {
+Unit *unit_new(Manager *m, size_t size) {
         Unit *u;
 
         assert(m);
+        assert(size >= sizeof(Meta));
 
-        if (!(u = new0(Unit, 1)))
+        u = malloc0(size);
+        if (!u)
                 return NULL;
 
-        if (!(u->meta.names = set_new(string_hash_func, string_compare_func))) {
+        u->meta.names = set_new(string_hash_func, string_compare_func);
+        if (!u->meta.names) {
                 free(u);
                 return NULL;
         }
diff --git a/src/unit.h b/src/unit.h
index 19314d6fbdd..626bdc43af6 100644
--- a/src/unit.h
+++ b/src/unit.h
@@ -286,6 +286,9 @@ union Unit {
 struct UnitVTable {
         const char *suffix;
 
+        /* How much memory does an object of this unit type need */
+        size_t object_size;
+
         /* Config file sections this unit type understands, separated
          * by NUL chars */
         const char *sections;
@@ -435,7 +438,7 @@ DEFINE_CAST(SNAPSHOT, Snapshot);
 DEFINE_CAST(SWAP, Swap);
 DEFINE_CAST(PATH, Path);
 
-Unit *unit_new(Manager *m);
+Unit *unit_new(Manager *m, size_t size);
 void unit_free(Unit *u);
 
 int unit_add_name(Unit *u, const char *name);