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Date: Tue, 28 Sep 2010 16:09:38 +0530 From: Balbir Singh <balbir@...ux.vnet.ibm.com> To: Martin Schwidefsky <schwidefsky@...ibm.com> Cc: Oleg Nesterov <oleg@...hat.com>, Michael Holzheu <holzheu@...ux.vnet.ibm.com>, Shailabh Nagar <nagar1234@...ibm.com>, Andrew Morton <akpm@...ux-foundation.org>, Venkatesh Pallipadi <venki@...gle.com>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Suresh Siddha <suresh.b.siddha@...el.com>, John stultz <johnstul@...ibm.com>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>, Heiko Carstens <heiko.carstens@...ibm.com>, linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [RFC][PATCH 09/10] taskstats: Fix exit CPU time accounting * Martin Schwidefsky <schwidefsky@...ibm.com> [2010-09-28 12:36:25]: > On Tue, 28 Sep 2010 14:53:55 +0530 > Balbir Singh <balbir@...ux.vnet.ibm.com> wrote: > > > * Martin Schwidefsky <schwidefsky@...ibm.com> [2010-09-28 11:08:28]: > > > > > On Tue, 28 Sep 2010 14:06:02 +0530 > > > Balbir Singh <balbir@...ux.vnet.ibm.com> wrote: > > > > > > > * Martin Schwidefsky <schwidefsky@...ibm.com> [2010-09-27 15:42:57]: > > > > > Got the part about self-reaping processes. But there is another issue: > > > > > consider an exiting thread where the group leader is still active. > > > > > The time for the thread will be added to the utime/stime fields in > > > > > the signal structure. Taskstats will happily ignore that time while > > > > > the group leader is still running. > > > > > > > > > > > > > Why do you say that? Not sure your comment is very clean, in > > > > fill_tgid, we do > > > > > > > > 1. Accumulate signal stats (contains stats for dead threads) > > > > 2. Accumulate stats for current threads > > > > > > > > fill_tgid_exit does something similar > > > > > > Hmm, I can't find anything in the code where the tsk->signal->{utime,stime} > > > > That is left to the actual subsystem (I should have been clearer in > > stating that the limitation is not with the taskstats infrastructure > > itself). Yes, your observation is indeed correct. > > > > taskstats code is expected to contain the callback for the subsystems > > it supports. delayacct() already does the right thing today, AFAICS > > > > > gets transferred to the taskstats record. There is a loop in fill_tgid over > > > the threads of the process but all it does is to call delayacct_add_tsk. > > > And that function does nothing with the cpu time of dead threads which is > > > stored in the signal structure. In addition which taskstats field is > > > supposed to contain the cpu time of the dead thread, ac_utime/ac_stime? > > > > > > > I've not focused much on ac_*, The changes that need to occur are we > > need to get the tsacct.c callbacks into taskstats. > > Ok, so tsacct.c is the right place to implement it. We will need new fields > in struct taskstats to contain the tsk->signal->{utime,stime} and some code > in bacct_add_tsk to do the copy. Agreed ? > Yes, the caveat though is that tsacct.c or xacct was not designed to provide notifications for tgid exit or provide tgid data. I don't recollect why they decided to go down that path or if there are some limitations that affect it. -- Three Cheers, Balbir -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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