Messages in this thread | | | Date | Thu, 25 Apr 2013 18:19:11 -0500 | From | Jacob Shin <> | Subject | Re: [PATCH V2 1/4] perf: Add hardware breakpoint address mask |
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On Thu, Apr 25, 2013 at 10:17:35AM -0700, H. Peter Anvin wrote: > On 04/25/2013 10:06 AM, Oleg Nesterov wrote: > >> > >> The downside is that in userland perf tool we need differing documentation > >> on what the mask syntax means for each architecture. > > > > Personally I think this is acceptable. > > > > But I am new to this code, so... > > > > That would seem really, really awkward. Yes, perf has a bunch of > low-level stuff, but it would seem highly undesirable to force the user > to deal with something like that. > > It would be good to have a user-friendly syntax that covers most of what > users may want to do and perhaps a longer form that can express > everything including ARM's byte selects; if the system can't honor the > request it should return an error.
Okay,
If arch specific masks are a no go, then I think I'm convinced that Oleg's idea of using bp_len is the right thing to do. Right now perf userland tool hard codes bp_len to 4, so I need to modify it to allow user to override the length if desired.
Oleg, Frederic, et al.
Which syntax do you prefer?
If we want to set bp_len to 16:
$ perf stat -e mem:0x1000:rw:16
Or
$ perf stat -e mem:0x1000:16
Or
$ perf stat -e mem:0x1000/16
If no bp_len value is specified, it will still default to 4 as it did before.
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