From: Shailabh Nagar Date: Fri, 14 Jul 2006 07:24:46 +0000 (-0700) Subject: [PATCH] per-task delay accounting: avoid send without listeners X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=c8924363da07aec213e5d359f23eeae1fff91951;p=openwrt%2Fstaging%2Fblogic.git [PATCH] per-task delay accounting: avoid send without listeners 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 Signed-off-by: Shailabh Nagar Cc: Jay Lan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/include/linux/taskstats_kern.h b/include/linux/taskstats_kern.h index 0ae8f67af1fd..2b6adec3a2e4 100644 --- a/include/linux/taskstats_kern.h +++ b/include/linux/taskstats_kern.h @@ -9,6 +9,7 @@ #include #include +#include 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)