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[PATCH 3/6] Add probes for malloc arena changes.
- From: Alexandre Oliva <aoliva at redhat dot com>
- To: libc-alpha at sourceware dot org
- Cc: carlos at redhat dot com, aj at suse dot com
- Date: Thu, 19 Sep 2013 12:09:51 -0300
- Subject: [PATCH 3/6] Add probes for malloc arena changes.
- Authentication-results: sourceware.org; auth=none
- References: <523B05A1 dot 4060009 at redhat dot com>
for ChangeLog
* malloc/arena.c (get_free_list): Add probe
memory_arena_reuse_free_list.
(reused_arena) [PER_THREAD]: Add probes memory_arena_reuse_wait
and memory_arena_reuse.
(arena_get2) [!PER_THREAD]: Likewise.
* malloc/malloc.c (__libc_realloc) [!PER_THREAD]: Add probe
memory_arena_reuse_realloc.
* manual/probes.texi: Document them.
---
malloc/arena.c | 5 ++++
malloc/malloc.c | 1 +
manual/probes.texi | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 66 insertions(+)
diff --git a/malloc/arena.c b/malloc/arena.c
index 0822fc8..89e8b92 100644
--- a/malloc/arena.c
+++ b/malloc/arena.c
@@ -775,6 +775,7 @@ get_free_list (void)
if (result != NULL)
{
+ LIBC_PROBE (memory_arena_reuse_free_list, 1, result);
(void)mutex_lock(&result->mutex);
tsd_setspecific(arena_key, (void *)result);
THREAD_STAT(++(result->stat_lock_loop));
@@ -811,9 +812,11 @@ reused_arena (mstate avoid_arena)
result = result->next;
/* No arena available. Wait for the next in line. */
+ LIBC_PROBE (memory_arena_reuse_wait, 3, &result->mutex, result, avoid_arena);
(void)mutex_lock(&result->mutex);
out:
+ LIBC_PROBE (memory_arena_reuse, 2, result, avoid_arena);
tsd_setspecific(arena_key, (void *)result);
THREAD_STAT(++(result->stat_lock_loop));
next_to_use = result->next;
@@ -892,6 +895,7 @@ arena_get2(mstate a_tsd, size_t size, mstate avoid_arena)
if (retried)
(void)mutex_unlock(&list_lock);
THREAD_STAT(++(a->stat_lock_loop));
+ LIBC_PROBE (memory_arena_reuse, 2, a, a_tsd);
tsd_setspecific(arena_key, (void *)a);
return a;
}
@@ -904,6 +908,7 @@ arena_get2(mstate a_tsd, size_t size, mstate avoid_arena)
locks. */
if(!retried && mutex_trylock(&list_lock)) {
/* We will block to not run in a busy loop. */
+ LIBC_PROBE (memory_arena_reuse_wait, 3, &list_lock, NULL, a_tsd);
(void)mutex_lock(&list_lock);
/* Since we blocked there might be an arena available now. */
diff --git a/malloc/malloc.c b/malloc/malloc.c
index 8f1ddf3..c5b3c7c 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -2977,6 +2977,7 @@ __libc_realloc(void* oldmem, size_t bytes)
#endif
#if !defined PER_THREAD
+ LIBC_PROBE (memory_arena_reuse_realloc, 1, ar_ptr);
/* As in malloc(), remember this arena for the next allocation. */
tsd_setspecific(arena_key, (void *)ar_ptr);
#endif
diff --git a/manual/probes.texi b/manual/probes.texi
index 37fd2f85..73b6158 100644
--- a/manual/probes.texi
+++ b/manual/probes.texi
@@ -33,6 +33,66 @@ located at @var{$arg1}, within a newly-allocated heap big enough to hold
at least @var{$arg2} bytes.
@end deftp
+@deftp Probe memory_arena_reuse (void *@var{$arg1}, void *@var{$arg2})
+This probe is hit when @code{malloc} has just selected an existing arena
+to reuse, and (temporarily) reserved it for exclusive use. Argument
+@var{$arg1} is a pointer to the newly-selected arena, and @var{$arg2} is
+a pointer to the arena previously used by that thread.
+
+When per-thread arenas are enabled, this occurs within
+@code{reused_arena}, right after the mutex mentioned in probe
+@code{memory_arena_reuse_wait} is acquired; argument @var{$arg1} will
+point to the same arena. In this configuration, this will usually only
+occur once per thread. The exception is when a thread first selected
+the main arena, but a subsequent allocation from it fails: then, and
+only then, may we switch to another arena to retry that allocations, and
+for further allocations within that thread.
+
+When per-thread arenas are disabled, this occurs within
+@code{arena_get2}, whenever the mutex for the previously-selected arena
+cannot be immediately acquired.
+@end deftp
+
+@deftp Probe memory_arena_reuse_wait (void *@var{$arg1}, void *@var{$arg2}, void *@var{$arg3})
+This probe is hit when @code{malloc} is about to wait for an arena to
+become available for reuse. Argument @var{$arg1} holds a pointer to the
+mutex the thread is going to wait on, @var{$arg2} is a pointer to a
+newly-chosen arena to be reused, and @var{$arg3} is a pointer to the
+arena previously used by that thread.
+
+When per-thread arenas are enabled, this occurs within
+@code{reused_arena}, when a thread first tries to allocate memory or
+needs a retry after a failure to allocate from the main arena, there
+isn't any free arena, the maximum number of arenas has been reached, and
+an existing arena was chosen for reuse, but its mutex could not be
+immediately acquired. The mutex in @var{$arg1} is the mutex of the
+selected arena.
+
+When per-thread arenas are disabled, this occurs within
+@code{arena_get2}, when a thread first tries to allocate memory or the
+mutex of the arena it previously used could not be immediately acquired,
+and none of the existing arenas could be immediately reserved for
+exclusive use. The mutex in @var{$arg1} is that of the list of arenas,
+and since the arena won't have been selected yet, @var{$arg2} will be
+@code{NULL}.
+@end deftp
+
+@deftp Probe memory_arena_reuse_free_list (void *@var{$arg1})
+This probe is hit when @code{malloc} has chosen an arena that is in the
+free list for use by a thread, within the @code{get_free_list} function.
+This probe is only available when @code{malloc} is configured to use
+per-thread arenas. The argument @var{$arg1} holds a pointer to the
+selected arena.
+@end deftp
+
+@deftp Probe memory_arena_reuse_realloc (void *@var{$arg1})
+This probe is hit within @code{realloc}, as the arena of the current
+thread is changed to match that in which the given address was
+allocated. This probe is not available when @code{malloc} is configured
+to use per-thread arenas. The argument @var{$arg1} holds a pointer to
+the newly-selected arena.
+@end deftp
+
@deftp Probe memory_mallopt (int @var{$arg1}, int @var{$arg2})
This probe is hit when function @code{mallopt} is called to change
@code{malloc} internal configuration parameters, before any change to