perf symbols: Rename kthreads to kmaps, using another abstraction for it

Using a struct thread instance just to hold the kernel space maps
(vmlinux + modules) is overkill and confuses people trying to
understand the perf symbols abstractions.

The kernel maps are really present in all threads, i.e. the kernel
is a library, not a separate thread.

So introduce the 'map_groups' abstraction and use it for the kernel
maps, now in the kmaps global variable.

It, in turn, will move, together with the threads list to the
perf_file abstraction, so that we can support multiple perf_file
instances, needed by perf diff.

Brainstormed-with: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <1260550239-5372-1-git-send-email-acme@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

5 files changed, 105 insertions, 84 deletions

diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
index 4dcecafa85d..ba0de90cd3d 100644
--- a/tools/perf/util/event.c
+++ b/tools/perf/util/event.c
@@ -254,13 +254,14 @@ void thread__find_addr_location(struct thread *self, u8 cpumode,
                                 struct addr_location *al,
                                 symbol_filter_t filter)
 {
-        struct thread *thread = al->thread = self;
+        struct map_groups *mg = &self->mg;
 
+        al->thread = self;
         al->addr = addr;
 
         if (cpumode & PERF_RECORD_MISC_KERNEL) {
                 al->level = 'k';
-                thread = kthread;
+                mg = kmaps;
         } else if (cpumode & PERF_RECORD_MISC_USER)
                 al->level = '.';
         else {
@@ -270,7 +271,7 @@ void thread__find_addr_location(struct thread *self, u8 cpumode,
                 return;
         }
 try_again:
-        al->map = thread__find_map(thread, type, al->addr);
+        al->map = map_groups__find(mg, type, al->addr);
         if (al->map == NULL) {
                 /*
                  * If this is outside of all known maps, and is a negative
@@ -281,8 +282,8 @@ try_again:
                  * "[vdso]" dso, but for now lets use the old trick of looking
                  * in the whole kernel symbol list.
                  */
-                if ((long long)al->addr < 0 && thread != kthread) {
-                        thread = kthread;
+                if ((long long)al->addr < 0 && mg != kmaps) {
+                        mg = kmaps;
                         goto try_again;
                 }
                 al->sym = NULL;
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index e7508ad3450..93620234294 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -29,11 +29,11 @@ enum dso_origin {
 };
 
 static void dsos__add(struct list_head *head, struct dso *dso);
-static struct map *thread__find_map_by_name(struct thread *self, char *name);
+static struct map *map_groups__find_by_name(struct map_groups *self, char *name);
 static struct map *map__new2(u64 start, struct dso *dso, enum map_type type);
 struct symbol *dso__find_symbol(struct dso *self, enum map_type type, u64 addr);
 static int dso__load_kernel_sym(struct dso *self, struct map *map,
-                                struct thread *thread, symbol_filter_t filter);
+                                struct map_groups *mg, symbol_filter_t filter);
 unsigned int symbol__priv_size;
 static int vmlinux_path__nr_entries;
 static char **vmlinux_path;
@@ -43,8 +43,8 @@ static struct symbol_conf symbol_conf__defaults = {
         .try_vmlinux_path = true,
 };
 
-static struct thread kthread_mem;
-struct thread *kthread = &kthread_mem;
+static struct map_groups kmaps_mem;
+struct map_groups *kmaps = &kmaps_mem;
 
 bool dso__loaded(const struct dso *self, enum map_type type)
 {
@@ -79,7 +79,7 @@ static void symbols__fixup_end(struct rb_root *self)
                 curr->end = roundup(curr->start, 4096);
 }
 
-static void __thread__fixup_maps_end(struct thread *self, enum map_type type)
+static void __map_groups__fixup_end(struct map_groups *self, enum map_type type)
 {
         struct map *prev, *curr;
         struct rb_node *nd, *prevnd = rb_first(&self->maps[type]);
@@ -102,11 +102,11 @@ static void __thread__fixup_maps_end(struct thread *self, enum map_type type)
         curr->end = ~0UL;
 }
 
-static void thread__fixup_maps_end(struct thread *self)
+static void map_groups__fixup_end(struct map_groups *self)
 {
         int i;
         for (i = 0; i < MAP__NR_TYPES; ++i)
-                __thread__fixup_maps_end(self, i);
+                __map_groups__fixup_end(self, i);
 }
 
 static struct symbol *symbol__new(u64 start, u64 len, const char *name)
@@ -364,8 +364,8 @@ out_failure:
  * kernel range is broken in several maps, named [kernel].N, as we don't have
  * the original ELF section names vmlinux have.
  */
-static int dso__split_kallsyms(struct dso *self, struct map *map, struct thread *thread,
-                               symbol_filter_t filter)
+static int dso__split_kallsyms(struct dso *self, struct map *map,
+                               struct map_groups *mg, symbol_filter_t filter)
 {
         struct map *curr_map = map;
         struct symbol *pos;
@@ -382,13 +382,13 @@ static int dso__split_kallsyms(struct dso *self, struct map *map, struct thread
 
                 module = strchr(pos->name, '\t');
                 if (module) {
-                        if (!thread->use_modules)
+                        if (!mg->use_modules)
                                 goto discard_symbol;
 
                         *module++ = '\0';
 
                         if (strcmp(self->name, module)) {
-                                curr_map = thread__find_map_by_name(thread, module);
+                                curr_map = map_groups__find_by_name(mg, module);
                                 if (curr_map == NULL) {
                                         pr_debug("/proc/{kallsyms,modules} "
                                                  "inconsistency!\n");
@@ -419,7 +419,7 @@ static int dso__split_kallsyms(struct dso *self, struct map *map, struct thread
                         }
 
                         curr_map->map_ip = curr_map->unmap_ip = identity__map_ip;
-                        __thread__insert_map(thread, curr_map);
+                        map_groups__insert(mg, curr_map);
                         ++kernel_range;
                 }
 
@@ -440,7 +440,7 @@ discard_symbol:		rb_erase(&pos->rb_node, root);
 
 
 static int dso__load_kallsyms(struct dso *self, struct map *map,
-                              struct thread *thread, symbol_filter_t filter)
+                              struct map_groups *mg, symbol_filter_t filter)
 {
         if (dso__load_all_kallsyms(self, map) < 0)
                 return -1;
@@ -448,13 +448,13 @@ static int dso__load_kallsyms(struct dso *self, struct map *map,
         symbols__fixup_end(&self->symbols[map->type]);
         self->origin = DSO__ORIG_KERNEL;
 
-        return dso__split_kallsyms(self, map, thread, filter);
+        return dso__split_kallsyms(self, map, mg, filter);
 }
 
 size_t kernel_maps__fprintf(FILE *fp)
 {
         size_t printed = fprintf(fp, "Kernel maps:\n");
-        printed += thread__fprintf_maps(kthread, fp);
+        printed += map_groups__fprintf_maps(kmaps, fp);
         return printed + fprintf(fp, "END kernel maps\n");
 }
 
@@ -745,7 +745,7 @@ out:
 }
 
 static int dso__load_sym(struct dso *self, struct map *map,
-                         struct thread *thread, const char *name, int fd,
+                         struct map_groups *mg, const char *name, int fd,
                          symbol_filter_t filter, int kernel, int kmodule)
 {
         struct map *curr_map = map;
@@ -849,7 +849,7 @@ static int dso__load_sym(struct dso *self, struct map *map,
                         snprintf(dso_name, sizeof(dso_name),
                                  "%s%s", self->short_name, section_name);
 
-                        curr_map = thread__find_map_by_name(thread, dso_name);
+                        curr_map = map_groups__find_by_name(mg, dso_name);
                         if (curr_map == NULL) {
                                 u64 start = sym.st_value;
 
@@ -868,7 +868,7 @@ static int dso__load_sym(struct dso *self, struct map *map,
                                 curr_map->map_ip = identity__map_ip;
                                 curr_map->unmap_ip = identity__map_ip;
                                 curr_dso->origin = DSO__ORIG_KERNEL;
-                                __thread__insert_map(kthread, curr_map);
+                                map_groups__insert(kmaps, curr_map);
                                 dsos__add(&dsos__kernel, curr_dso);
                         } else
                                 curr_dso = curr_map->dso;
@@ -1094,7 +1094,7 @@ int dso__load(struct dso *self, struct map *map, symbol_filter_t filter)
         dso__set_loaded(self, map->type);
 
         if (self->kernel)
-                return dso__load_kernel_sym(self, map, kthread, filter);
+                return dso__load_kernel_sym(self, map, kmaps, filter);
 
         name = malloc(size);
         if (!name)
@@ -1180,7 +1180,7 @@ out:
         return ret;
 }
 
-static struct map *thread__find_map_by_name(struct thread *self, char *name)
+static struct map *map_groups__find_by_name(struct map_groups *self, char *name)
 {
         struct rb_node *nd;
 
@@ -1228,7 +1228,7 @@ static int dsos__set_modules_path_dir(char *dirname)
                                  (int)(dot - dent->d_name), dent->d_name);
 
                         strxfrchar(dso_name, '-', '_');
-                        map = thread__find_map_by_name(kthread, dso_name);
+                        map = map_groups__find_by_name(kmaps, dso_name);
                         if (map == NULL)
                                 continue;
 
@@ -1281,7 +1281,7 @@ static struct map *map__new2(u64 start, struct dso *dso, enum map_type type)
         return self;
 }
 
-static int thread__create_module_maps(struct thread *self)
+static int map_groups__create_module_maps(struct map_groups *self)
 {
         char *line = NULL;
         size_t n;
@@ -1338,7 +1338,7 @@ static int thread__create_module_maps(struct thread *self)
                         dso->has_build_id = true;
 
                 dso->origin = DSO__ORIG_KMODULE;
-                __thread__insert_map(self, map);
+                map_groups__insert(self, map);
                 dsos__add(&dsos__kernel, dso);
         }
 
@@ -1353,7 +1353,8 @@ out_failure:
         return -1;
 }
 
-static int dso__load_vmlinux(struct dso *self, struct map *map, struct thread *thread,
+static int dso__load_vmlinux(struct dso *self, struct map *map,
+                             struct map_groups *mg,
                              const char *vmlinux, symbol_filter_t filter)
 {
         int err = -1, fd;
@@ -1387,14 +1388,14 @@ static int dso__load_vmlinux(struct dso *self, struct map *map, struct thread *t
                 return -1;
 
         dso__set_loaded(self, map->type);
-        err = dso__load_sym(self, map, thread, self->long_name, fd, filter, 1, 0);
+        err = dso__load_sym(self, map, mg, self->long_name, fd, filter, 1, 0);
         close(fd);
 
         return err;
 }
 
 static int dso__load_kernel_sym(struct dso *self, struct map *map,
-                                struct thread *thread, symbol_filter_t filter)
+                                struct map_groups *mg, symbol_filter_t filter)
 {
         int err;
         bool is_kallsyms;
@@ -1404,7 +1405,7 @@ static int dso__load_kernel_sym(struct dso *self, struct map *map,
                 pr_debug("Looking at the vmlinux_path (%d entries long)\n",
                          vmlinux_path__nr_entries);
                 for (i = 0; i < vmlinux_path__nr_entries; ++i) {
-                        err = dso__load_vmlinux(self, map, thread,
+                        err = dso__load_vmlinux(self, map, mg,
                                                 vmlinux_path[i], filter);
                         if (err > 0) {
                                 pr_debug("Using %s for symbols\n",
@@ -1420,12 +1421,12 @@ static int dso__load_kernel_sym(struct dso *self, struct map *map,
         if (is_kallsyms)
                 goto do_kallsyms;
 
-        err = dso__load_vmlinux(self, map, thread, self->long_name, filter);
+        err = dso__load_vmlinux(self, map, mg, self->long_name, filter);
         if (err <= 0) {
                 pr_info("The file %s cannot be used, "
                         "trying to use /proc/kallsyms...", self->long_name);
 do_kallsyms:
-                err = dso__load_kallsyms(self, map, thread, filter);
+                err = dso__load_kallsyms(self, map, mg, filter);
                 if (err > 0 && !is_kallsyms)
                         dso__set_long_name(self, strdup("[kernel.kallsyms]"));
         }
@@ -1508,7 +1509,7 @@ size_t dsos__fprintf_buildid(FILE *fp)
                 __dsos__fprintf_buildid(&dsos__user, fp));
 }
 
-static int thread__create_kernel_map(struct thread *self, const char *vmlinux)
+static int map_groups__create_kernel_map(struct map_groups *self, const char *vmlinux)
 {
         struct map *kmap;
         struct dso *kernel = dso__new(vmlinux ?: "[kernel.kallsyms]");
@@ -1533,7 +1534,7 @@ static int thread__create_kernel_map(struct thread *self, const char *vmlinux)
                                  sizeof(kernel->build_id)) == 0)
                 kernel->has_build_id = true;
 
-        __thread__insert_map(self, kmap);
+        map_groups__insert(self, kmap);
         dsos__add(&dsos__kernel, kernel);
         dsos__add(&dsos__user, vdso);
 
@@ -1607,23 +1608,23 @@ int symbol__init(struct symbol_conf *conf)
 
         elf_version(EV_CURRENT);
         symbol__priv_size = pconf->priv_size;
-        thread__init(kthread, 0);
+        map_groups__init(kmaps);
 
         if (pconf->try_vmlinux_path && vmlinux_path__init() < 0)
                 return -1;
 
-        if (thread__create_kernel_map(kthread, pconf->vmlinux_name) < 0) {
+        if (map_groups__create_kernel_map(kmaps, pconf->vmlinux_name) < 0) {
                 vmlinux_path__exit();
                 return -1;
         }
 
-        kthread->use_modules = pconf->use_modules;
-        if (pconf->use_modules && thread__create_module_maps(kthread) < 0)
+        kmaps->use_modules = pconf->use_modules;
+        if (pconf->use_modules && map_groups__create_module_maps(kmaps) < 0)
                 pr_debug("Failed to load list of modules in use, "
                          "continuing...\n");
         /*
          * Now that we have all the maps created, just set the ->end of them:
          */
-        thread__fixup_maps_end(kthread);
+        map_groups__fixup_end(kmaps);
         return 0;
 }
diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
index 17003efa0b3..6e1da1ea631 100644
--- a/tools/perf/util/symbol.h
+++ b/tools/perf/util/symbol.h
@@ -113,8 +113,8 @@ size_t kernel_maps__fprintf(FILE *fp);
 
 int symbol__init(struct symbol_conf *conf);
 
-struct thread;
-struct thread *kthread;
+struct map_groups;
+struct map_groups *kmaps;
 extern struct list_head dsos__user, dsos__kernel;
 extern struct dso *vdso;
 #endif /* __PERF_SYMBOL */
diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
index 603f5610861..a1285129c83 100644
--- a/tools/perf/util/thread.c
+++ b/tools/perf/util/thread.c
@@ -9,11 +9,9 @@
 static struct rb_root threads;
 static struct thread *last_match;
 
-void thread__init(struct thread *self, pid_t pid)
+void map_groups__init(struct map_groups *self)
 {
         int i;
-        self->pid = pid;
-        self->comm = NULL;
         for (i = 0; i < MAP__NR_TYPES; ++i) {
                 self->maps[i] = RB_ROOT;
                 INIT_LIST_HEAD(&self->removed_maps[i]);
@@ -25,7 +23,8 @@ static struct thread *thread__new(pid_t pid)
         struct thread *self = zalloc(sizeof(*self));
 
         if (self != NULL) {
-                thread__init(self, pid);
+                map_groups__init(&self->mg);
+                self->pid = pid;
                 self->comm = malloc(32);
                 if (self->comm)
                         snprintf(self->comm, 32, ":%d", self->pid);
@@ -57,8 +56,8 @@ static const char *map_type__name[MAP__NR_TYPES] = {
         [MAP__FUNCTION] = "Functions",
 };
 
-static size_t __thread__fprintf_maps(struct thread *self,
-                                     enum map_type type, FILE *fp)
+static size_t __map_groups__fprintf_maps(struct map_groups *self,
+                                         enum map_type type, FILE *fp)
 {
         size_t printed = fprintf(fp, "%s:\n", map_type__name[type]);
         struct rb_node *nd;
@@ -76,16 +75,16 @@ static size_t __thread__fprintf_maps(struct thread *self,
         return printed;
 }
 
-size_t thread__fprintf_maps(struct thread *self, FILE *fp)
+size_t map_groups__fprintf_maps(struct map_groups *self, FILE *fp)
 {
         size_t printed = 0, i;
         for (i = 0; i < MAP__NR_TYPES; ++i)
-                printed += __thread__fprintf_maps(self, i, fp);
+                printed += __map_groups__fprintf_maps(self, i, fp);
         return printed;
 }
 
-static size_t __thread__fprintf_removed_maps(struct thread *self,
-                                             enum map_type type, FILE *fp)
+static size_t __map_groups__fprintf_removed_maps(struct map_groups *self,
+                                                 enum map_type type, FILE *fp)
 {
         struct map *pos;
         size_t printed = 0;
@@ -101,20 +100,25 @@ static size_t __thread__fprintf_removed_maps(struct thread *self,
         return printed;
 }
 
-static size_t thread__fprintf_removed_maps(struct thread *self, FILE *fp)
+static size_t map_groups__fprintf_removed_maps(struct map_groups *self, FILE *fp)
 {
         size_t printed = 0, i;
         for (i = 0; i < MAP__NR_TYPES; ++i)
-                printed += __thread__fprintf_removed_maps(self, i, fp);
+                printed += __map_groups__fprintf_removed_maps(self, i, fp);
         return printed;
 }
 
-static size_t thread__fprintf(struct thread *self, FILE *fp)
+static size_t map_groups__fprintf(struct map_groups *self, FILE *fp)
 {
-        size_t printed = fprintf(fp, "Thread %d %s\n", self->pid, self->comm);
-        printed += thread__fprintf_removed_maps(self, fp);
+        size_t printed = map_groups__fprintf_maps(self, fp);
         printed += fprintf(fp, "Removed maps:\n");
-        return printed + thread__fprintf_removed_maps(self, fp);
+        return printed + map_groups__fprintf_removed_maps(self, fp);
+}
+
+static size_t thread__fprintf(struct thread *self, FILE *fp)
+{
+        return fprintf(fp, "Thread %d %s\n", self->pid, self->comm) +
+               map_groups__fprintf(&self->mg, fp);
 }
 
 struct thread *threads__findnew(pid_t pid)
@@ -168,7 +172,8 @@ struct thread *register_idle_thread(void)
         return thread;
 }
 
-static void thread__remove_overlappings(struct thread *self, struct map *map)
+static void map_groups__remove_overlappings(struct map_groups *self,
+                                            struct map *map)
 {
         struct rb_root *root = &self->maps[map->type];
         struct rb_node *next = rb_first(root);
@@ -238,12 +243,15 @@ struct map *maps__find(struct rb_root *maps, u64 ip)
 
 void thread__insert_map(struct thread *self, struct map *map)
 {
-        thread__remove_overlappings(self, map);
-        maps__insert(&self->maps[map->type], map);
+        map_groups__remove_overlappings(&self->mg, map);
+        map_groups__insert(&self->mg, map);
 }
 
-static int thread__clone_maps(struct thread *self, struct thread *parent,
-                              enum map_type type)
+/*
+ * XXX This should not really _copy_ te maps, but refcount them.
+ */
+static int map_groups__clone(struct map_groups *self,
+                             struct map_groups *parent, enum map_type type)
 {
         struct rb_node *nd;
         for (nd = rb_first(&parent->maps[type]); nd; nd = rb_next(nd)) {
@@ -251,7 +259,7 @@ static int thread__clone_maps(struct thread *self, struct thread *parent,
                 struct map *new = map__clone(map);
                 if (new == NULL)
                         return -ENOMEM;
-                thread__insert_map(self, new);
+                map_groups__insert(self, new);
         }
         return 0;
 }
@@ -267,7 +275,7 @@ int thread__fork(struct thread *self, struct thread *parent)
                 return -ENOMEM;
 
         for (i = 0; i < MAP__NR_TYPES; ++i)
-                if (thread__clone_maps(self, parent, i) < 0)
+                if (map_groups__clone(&self->mg, &parent->mg, i) < 0)
                         return -ENOMEM;
         return 0;
 }
@@ -286,11 +294,11 @@ size_t threads__fprintf(FILE *fp)
         return ret;
 }
 
-struct symbol *thread__find_symbol(struct thread *self,
-                                   enum map_type type, u64 addr,
-                                   symbol_filter_t filter)
+struct symbol *map_groups__find_symbol(struct map_groups *self,
+                                       enum map_type type, u64 addr,
+                                       symbol_filter_t filter)
 {
-        struct map *map = thread__find_map(self, type, addr);
+        struct map *map = map_groups__find(self, type, addr);
 
         if (map != NULL)
                 return map__find_symbol(map, map->map_ip(map, addr), filter);
diff --git a/tools/perf/util/thread.h b/tools/perf/util/thread.h
index 686d6e914d9..a6333f3716a 100644
--- a/tools/perf/util/thread.h
+++ b/tools/perf/util/thread.h
@@ -5,52 +5,63 @@
 #include <unistd.h>
 #include "symbol.h"
 
-struct thread {
-        struct rb_node          rb_node;
+struct map_groups {
         struct rb_root          maps[MAP__NR_TYPES];
         struct list_head        removed_maps[MAP__NR_TYPES];
-        pid_t                   pid;
         bool                    use_modules;
+};
+
+struct thread {
+        struct rb_node          rb_node;
+        struct map_groups       mg;
+        pid_t                   pid;
         char                    shortname[3];
         char                    *comm;
         int                     comm_len;
 };
 
-void thread__init(struct thread *self, pid_t pid);
+void map_groups__init(struct map_groups *self);
 int thread__set_comm(struct thread *self, const char *comm);
 int thread__comm_len(struct thread *self);
 struct thread *threads__findnew(pid_t pid);
 struct thread *register_idle_thread(void);
 void thread__insert_map(struct thread *self, struct map *map);
 int thread__fork(struct thread *self, struct thread *parent);
-size_t thread__fprintf_maps(struct thread *self, FILE *fp);
+size_t map_groups__fprintf_maps(struct map_groups *self, FILE *fp);
 size_t threads__fprintf(FILE *fp);
 
 void maps__insert(struct rb_root *maps, struct map *map);
 struct map *maps__find(struct rb_root *maps, u64 addr);
 
-static inline struct map *thread__find_map(struct thread *self,
+static inline void map_groups__insert(struct map_groups *self, struct map *map)
+{
+         maps__insert(&self->maps[map->type], map);
+}
+
+static inline struct map *map_groups__find(struct map_groups *self,
                                            enum map_type type, u64 addr)
 {
-        return self ? maps__find(&self->maps[type], addr) : NULL;
+        return maps__find(&self->maps[type], addr);
 }
 
-static inline void __thread__insert_map(struct thread *self, struct map *map)
+static inline struct map *thread__find_map(struct thread *self,
+                                           enum map_type type, u64 addr)
 {
-         maps__insert(&self->maps[map->type], map);
+        return self ? map_groups__find(&self->mg, type, addr) : NULL;
 }
 
 void thread__find_addr_location(struct thread *self, u8 cpumode,
                                 enum map_type type, u64 addr,
                                 struct addr_location *al,
                                 symbol_filter_t filter);
-struct symbol *thread__find_symbol(struct thread *self,
-                                   enum map_type type, u64 addr,
-                                   symbol_filter_t filter);
+struct symbol *map_groups__find_symbol(struct map_groups *self,
+                                       enum map_type type, u64 addr,
+                                       symbol_filter_t filter);
 
 static inline struct symbol *
-thread__find_function(struct thread *self, u64 addr, symbol_filter_t filter)
+map_groups__find_function(struct map_groups *self, u64 addr,
+                          symbol_filter_t filter)
 {
-        return thread__find_symbol(self, MAP__FUNCTION, addr, filter);
+        return map_groups__find_symbol(self, MAP__FUNCTION, addr, filter);
 }
 #endif  /* __PERF_THREAD_H */