Messages in this thread | | | Date | Fri, 2 Jan 2009 22:28:02 +0100 | From | Frederic Weisbecker <> | Subject | Re: [PATCH] tracing/function-graph-tracer: tracing only syscalls mode |
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On Fri, Jan 02, 2009 at 08:40:14PM +0100, Ingo Molnar wrote: > > * Frederic Weisbecker <fweisbec@gmail.com> wrote: > > > Impact: make more easy the syscalls tracing > > > > This patch extends to syscalls the features which let one to trace > > only one ore more function (and those they call). > > This way we can get rid of the workqueues, kernel threads, softirqs from > > ksoftirqd and only have the syscall path on the trace. > > > > Note that hardirq that interrupt the syscalls are still traced. But we could > > add an option to disable the interrupt tracing as well in the future. > > > > To use this new feature: > > > > echo function_graph > /debugfs/tracing/current_tracer > > echo syscalls > /debugfs/tracing/set_graph_function > > nice. I think a key item is missing though: > > > @@ -1397,6 +1398,9 @@ asmregparm long syscall_trace_enter(struct pt_regs *regs) > > { > > long ret = 0; > > > > + /* Tell the function graph tracer we are entering a system call */ > > + ftrace_graph_syscall_enter(); > > We could actually trace the _syscalls_ themselves, a'la strace:
"a la" ? Oh pretty, those two words have been picked from french to english language :-) I didn't know.
Yes, these parameters displaying a la strace are in my projects, as well as the return value of the syscalls (and other functions later).
> munmap(0xb7ff3000, 4096) = 0 > > So instead of the current ftrace output: > > 0) cc1-30212 | | sys32_mmap2() { > 0) cc1-30212 | | down_write() { > 0) cc1-30212 | 0.272 us | _spin_lock_irq(); > 0) cc1-30212 | 0.969 us | } > 0) cc1-30212 | | do_mmap_pgoff() { > > We could get something like: > > 0) cc1-30212 | | sys32_mmap2(0xb7ff3000, 4096) { > 0) cc1-30212 | | down_write() { > 0) cc1-30212 | 0.272 us | _spin_lock_irq(); > 0) cc1-30212 | 0.969 us | } > 0) cc1-30212 | | do_mmap_pgoff() { > [...] > 0) cc1-30212 | + 22.537 us | } = 0 > > > Or maybe as separate trace entries: > > 0) cc1-30212 | |> sys32_mmap2 [0xb7ff3000, 4096] > 0) cc1-30212 | | sys32_mmap2 { > 0) cc1-30212 | | down_write() { > 0) cc1-30212 | 0.272 us | _spin_lock_irq(); > 0) cc1-30212 | 0.969 us | } > 0) cc1-30212 | | do_mmap_pgoff() { > [...] > 0) cc1-30212 | + 22.537 us | } > 0) cc1-30212 | |< sys32_mmap2 => 0 > > For that we'd have to pass in something like the syscall function address > (sys_call_table[regs->ax]), and the up to 6 parameters > [regs->bx,cx,dx,si,di,bp]. > > (and initially we could just print all of them i guess, instead of a > variable-width thing) > > We wouldnt do smart decoding of syscall arguments normally - just print > the raw arguments with no decoding. (like strace -e raw=all) > > How does this sound?
That sounds good. I just need a new entry type for this. I can pass all these registers on insertion and filter them by syscall number on output stage.
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