On Wed, 2010-12-01 at 19:51 +0100, Oleg Nesterov wrote: > But in fact I don't really understand this anyway. This is called > before we reparent our children. This means that ac_cutime/ac_cstime > can be changed after that (multithreading, or full_cdata_enabled). > > Say, taskstats_exit()->fill_stats()->bacct_add_tsk(). Every thread > does this, including the group_leader. But, it is possible that > group_leader exits first, before other threads. IOW, what > stats->ac_cXtime actually mean? Because I worked mostly with the ptop tool, I was not so much focused on the taskstats exit events, but instead more on the taskstats commands to query data for running tasks. For the query scenario stats->ac_cXtime means: 1) full_cdata=0: "Sum of CPU time of exited child processes where sys_wait() have been done (up to this time)" 2) full_cdata=1: "Sum of CPU time of exited child processes where sys_wait() have been done plus exited child processes where the parents ignored SIGCHLD or have set SA_NOCLDWAIT (up to this time)" Regarding taskstats_exit(): Do you have something like the following scenario in mind? 1) You have a thread group with several threads 2) Thread group leader dies and reports cdata_wait in taskstats_exit() 3) Thread group leader stays around as zombie until the thread group dies 4) Other forked processes of this thread group die 5) cdata_wait of thread group is increased 6) The new cdata is not reported by any exit event of the thread group So maybe we should remove the thread_group_leader() check and report cdata_wait for all threads and not only for the thread group leader? We also should add ac_tgid to taskstats so that userspace can find the corresponding thread group for each thread. When the last thread exits and the process/thread group dies, taskstats_exit() sends an additional taskstats struct to userspace that aggregates the thread accounting data. Currently only the delay accounting data is aggregated (see taskstats_exit->fill_tgid_exit->delayacct_add_tsk). Not sure, why the other information is not aggregated. We perhaps also should include ac_cXtime in the aggregated taskstats. Michael -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
