From: Balbir S. <ba...@in...> - 2006-05-09 17:31:18
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On Tue, May 09, 2006 at 06:20:12PM +1000, Nick Piggin wrote: > Balbir Singh wrote: > > >On Tue, May 09, 2006 at 03:57:06PM +1000, Nick Piggin wrote: > > > >>Well they'll be _collecting_ the stats, yes. Will they really be using > >>them for anything? > >> > > > >Hmm.. No, the statistics are sent down using the netlink interface > >to listeners on the netlink group (on every task exit) or to the task that > >actually requested for the delay accounting data. > > > >The stats are currently gathered in kernel and used by user space. > > > > So... what are the consumers of this data going to be? That is my question. More details on the consumers of this data is available at http://lkml.org/lkml/2006/3/13/367 > > >>If you make the whole thing much lighter weight for tasks which aren't > >>using the accounting, you have a better chance of people turning the > >>CONFIG option on. > >> > >> > > > >I am not sure I understand the point completely. Are you suggesting that > >struct task_delay_info be moved to common data structure as an aggregate > >containing all the delay stats data? > > > > My suggestion is basically this: if the accounting is going to be used > infrequently, it might be a good idea to allocate the accounting structures > on demand, and only perform the accounting when these structures are > allocated. > > It all adds up. Extra cache misses, more icache, more logic, etc... I > suspect > that relatively few people will care about these stats. > Thanks for clarifying. I now understand your suggestion better. The accounting is going to be frequent, with data from all tasks in the system being collected and processed frequently. Since the accounting is frequent, I think the current scheme works better than on-demand allocation. Regarding the usefulness of these stats, please see http://www.uwsg.iu.edu/hypermail/linux/kernel/0604.2/1731.html Balbir Singh, Linux Technology Center, IBM Software Labs |