The patch titled
per-task delay accounting: avoid send without listeners
has been added to the -mm tree. Its filename is
per-task-delay-accounting-avoid-send-without-listeners.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: per-task delay accounting: avoid send without listeners
From: Shailabh Nagar <nagar@xxxxxxxxxxxxxx>
Don't send taskstats (per-pid or per-tgid) on thread exit when no one is
listening for such data.
Currently the taskstats interface allocates a structure, fills it in and
calls netlink to send out per-pid and per-tgid stats regardless of whether
a userspace listener for the data exists (netlink layer would check for
that and avoid the multicast).
As a result of this patch, the check for the no-listener case is performed
early, avoiding the redundant allocation and filling up of the taskstats
structures.
Signed-off-by: Balbir Singh <balbir@xxxxxxxxxx>
Signed-off-by: Shailabh Nagar <nagar@xxxxxxxxxxxxxx>
Cc: Jay Lan <jlan@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
include/linux/taskstats_kern.h | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
diff -puN include/linux/taskstats_kern.h~per-task-delay-accounting-avoid-send-without-listeners include/linux/taskstats_kern.h
--- a/include/linux/taskstats_kern.h~per-task-delay-accounting-avoid-send-without-listeners
+++ a/include/linux/taskstats_kern.h
@@ -9,6 +9,7 @@
#include <linux/taskstats.h>
#include <linux/sched.h>
+#include <net/genetlink.h>
enum {
TASKSTATS_MSG_UNICAST, /* send data only to requester */
@@ -19,9 +20,19 @@ enum {
extern kmem_cache_t *taskstats_cache;
extern struct mutex taskstats_exit_mutex;
+static inline int taskstats_has_listeners(void)
+{
+ if (!genl_sock)
+ return 0;
+ return netlink_has_listeners(genl_sock, TASKSTATS_LISTEN_GROUP);
+}
+
+
static inline void taskstats_exit_alloc(struct taskstats **ptidstats)
{
- *ptidstats = kmem_cache_zalloc(taskstats_cache, SLAB_KERNEL);
+ *ptidstats = NULL;
+ if (taskstats_has_listeners())
+ *ptidstats = kmem_cache_zalloc(taskstats_cache, SLAB_KERNEL);
}
static inline void taskstats_exit_free(struct taskstats *tidstats)
_
Patches currently in -mm which might be from nagar@xxxxxxxxxxxxxx are
per-task-delay-accounting-setup.patch
per-task-delay-accounting-setup-fix-1.patch
per-task-delay-accounting-setup-fix-2.patch
per-task-delay-accounting-sync-block-i-o-and-swapin-delay-collection.patch
per-task-delay-accounting-sync-block-i-o-and-swapin-delay-collection-fix-1.patch
per-task-delay-accounting-cpu-delay-collection-via-schedstats.patch
per-task-delay-accounting-cpu-delay-collection-via-schedstats-fix-1.patch
per-task-delay-accounting-utilities-for-genetlink-usage.patch
per-task-delay-accounting-taskstats-interface-fix-1.patch
per-task-delay-accounting-documentation.patch
per-task-delay-accounting-proc-export-of-aggregated-block-i-o-delays.patch
per-task-delay-accounting-proc-export-of-aggregated-block-i-o-delays-warning-fix.patch
delay-accounting-taskstats-interface-send-tgid-once.patch
delay-accounting-taskstats-interface-send-tgid-once-fixes.patch
per-task-delay-accounting-avoid-send-without-listeners.patch
task-watchers-register-per-task-delay-accounting.patch
-
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