Messages in this thread | | | Date | Tue, 16 Nov 2010 10:23:06 +0100 | From | Jiri Olsa <> | Subject | Re: [PATCHv2 2/2] tracing,mm - add kernel pagefault tracepoint for x86 & x86_64 |
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On Mon, Nov 15, 2010 at 09:19:20AM -0500, Steven Rostedt wrote: > On Mon, 2010-11-15 at 14:43 +0100, Frederic Weisbecker wrote: > > > > dotraplinkage void __kprobes > > do_page_fault(struct pt_regs *regs, unsigned long error_code) > > { > > unsigned long address; > > > > /* Get the faulting address: */ > > address = read_cr2(); > > > > trace_mm_pagefault_start(address, error_code); > > __do_page_fault(regs, address, error_code); > > trace_mm_pagefault_end(address); > > } > > > > > > Would you be ok with that? > > > > Last thing I worry about is that error_code that is very arch dependent. > > If someone writes a script that depends on the x86 code, it won't work > > elsewhere while it's fairly possible to have a generic tracepoint there. > > > > So perhaps we rather need a generic enum field instead of the error_code, > > to express the most interesting specific fault attributes. Than can > > probably be added later though, once someone really needs it. > > > > Hm? > > Perhaps we should have: > > trace_arch_mm_pagefault_start(address, error_code); > __do_page_fault(regs, address, error_code); > trace_mm_pagefault_end(address); > > > Then we have a arch/x86/kernel/trace.c that can map trace_arch_... > events to generic events. This file will hold the > trace_mm_pagefault_start(), which is called by > trace_arch_mm_pagefault_start(). Have a hook that when the > trace_mm_pagefault_start() is enabled, we also enable > trace_arch_mm_pagefault_start() that calls this tracepoint. The > trace_mm_pagefault_start() will then translate the > trace_arch_mm_pagfault_start() into the generic trace_mm_pagefault_start > event with the generic error_code that all archs will use. > > Reason being, we don't need to do any extra processing in the fast path > when tracing is not enabled. > > Also, I'm going to start working on the stable ABI today. do you mean stable api for the hook you described above? or should I come up with smth..
thanks, jirka
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