Messages in this thread | | | Date | Tue, 21 Jul 2009 09:25:27 +0800 | From | Li Zefan <> | Subject | Re: [PATCH v2] tracing/filters: Improve subsystem filter |
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Steven Rostedt wrote: > On Mon, 20 Jul 2009, Steven Rostedt wrote: > >> >> On Mon, 20 Jul 2009, Li Zefan wrote: >> >>> Currently a subsystem filter should be applicable to all events >>> under the subsystem, and if it failed, all the event filters >>> will be cleared. Those behaviors make subsys filter much less >>> useful: >>> >>> # echo 'vec == 1' > irq/softirq_entry/filter >>> # echo 'irq == 5' > irq/filter >>> bash: echo: write error: Invalid argument >>> # cat irq/softirq_entry/filter >>> none >>> >>> I'd expect it set the filter for irq_handler_entry/exit, and >>> not touch softirq_entry/exit. >>> >>> The basic idea is, try to see if the filter can be applied >>> to which events, and then just apply to the those events: >>> >>> # echo 'vec == 1' > softirq_entry/filter >>> # echo 'irq == 5' > filter >>> # cat irq_handler_entry/filter >>> irq == 5 >>> # cat softirq_entry/filter >>> vec == 1 > > OK, I tried this and it worked as you described, but it also does > something that I did not like. Basically this: > > # echo 'vec == 1' > filter > # cat softirq_entry/filter > vec == 1 > # cat irq_handler_entry/filter > none > # cat filter > vec == 1 > # echo 'irq == 5' > filter > # cat irq_handler_entry/filter > irq == 5 > # cat softirq_entry/filter > vec == 1 > # cat filter > irq == 5 > > > That last "cat filter" should show: > vec == 1 > irq == 5 >
But I did not change the read semantic. For example, when subsystem filter is not set at all:
# echo 'irq == 5' > irq_handler_entry/filter # echo 'vec == 1' > softirq_entry/filter # cat filter none
It'll show "none".
> I can keep this version, since I do find it useful (I've now come to the > conclusion that having the filter work only for those filters that it > would work for is fine). But the top level filter should show all filters. >
As I said in an old mail, I think the subsystem filter is much more useful in "write" than in "read".
I have no strong option about its read semantic, but I can do what you like.
Suppose: irq_handler_entry/filter -> irq == 5 irq_handler_exit/filter -> none softirq_entry/filter -> vec == 1 softirq_exit/filter -> vec == 2
Proposal 1:
# cat filter irq == 5 vec == 1 vec == 2
Proposal 2:
# cat filter irq_handler_entry: irq == 5 irq_handler_exit: none softirq_entry: vec == 1 softirq_exit: vec == 2
Which do you think is better? Or do you have some better idea?
And in the failure case:
# echo 'irq == not_num' > filter bash: echo: write error: Invalid argument
1: # cat filter (still shows filters in each event like above)
or shows error message (the current behavior)
2: # cat filter irq == not_num ^ parse_error: Couldn't find or set field in one of a subsystem's events
?
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