Messages in this thread | | | Date | Fri, 09 Jun 2006 21:06:02 +0530 | From | Balbir Singh <> | Subject | Re: [Patch][RFC] Disabling per-tgid stats on task exit in taskstats |
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Andrew Morton wrote: > On Fri, 09 Jun 2006 16:21:46 +0530 > Balbir Singh <balbir@in.ibm.com> wrote: > > >>Andrew Morton wrote: >> >>>On Fri, 09 Jun 2006 03:41:04 -0400 >>>Shailabh Nagar <nagar@watson.ibm.com> wrote: >>> >>> >>> >>>>Hence, this patch introduces a configuration parameter >>>> /sys/kernel/taskstats_tgid_exit >>>>through which a privileged user can turn on/off sending of per-tgid stats on >>>>task exit. >>> >>> >>>That seems a bit clumsy. What happens if one consumer wants the per-tgid >>>stats and another does not? >> >>For all subsystems that re-use the taskstats structure from the exit path, >>we have the issue that you mentioned. Thats because several statistics co-exist >>in the same structure. These subsystems can keep their tgid-stats empty by not >>filling up anything in fill_tgid() or using this patch to selectively enable/disable >>tgid stats. >> >>For other subsystems, they could pass tgidstats as NULL to taskstats_exit_send(). >> > > > I don't understand. If a subsystem exists then it fills in its slots in > the taskstats structure, doesn't it? > > No other subsystem needs a global knob, does it? > > You see the problem - if one userspace package wants the tgid-stats and > another concurrently-running one does now, what do we do? Just leave it > enabled and run a bit slower?
Another option is to get the package to define their own taskstats genetlink attribute and fill it up in taskstats_exit_send(). This would be similar to TASKSTATS_TYPE_AGGR_PID/TGID.
They can make this attribute independent of the taskstats structure and fill it based on their policy (per-pid or per-tgid). But the current interface users like CSA want to build on top of the taskstats structure.
> > If so, how much slower? Your changelog says some potential users don't > need the tgid-stats, but so what? I assume this patch is a performance > thing? If so, has it been quantified? >
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Balbir Singh, Linux Technology Center, IBM Software Labs - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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