lkml.org 
[lkml]   [2008]   [Nov]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 3/3] tracing/function-return-tracer: add the overrun field

* Steven Rostedt <rostedt@goodmis.org> wrote:

>
> On Tue, 18 Nov 2008, Ingo Molnar wrote:
> > * Steven Rostedt <rostedt@goodmis.org> wrote:
> > >
> > > I was just looking at the stack tracer, and it pretty much gives us
> > > the answer ;-) I'm hitting on max traces around 55, but some of
> > > those are asm calls. We could do 50 or 60? We probably want to make
> > > sure that the two do not come close to hitting. That is, the bottom
> > > of the stack to overwrite the saved return addresses.
> >
> > does the stack tracer properly nest across IRQ entry boundaries
> > already on x86? We used to have problems in that area.
>
> Actually, because the stack tracer is in generic code, we punt on IRQ
> stacks:
>
> /* we do not handle interrupt stacks yet */
> if (!object_is_on_stack(&this_size))
> return;
>
> I check if the local variable "this_size" is on the current->stack
> and if it is not then this means that we are using some other stack,
> and we do not record it.
>
> What would be needed is to make a per-arch stack call. Perhaps have
> a:
>
> arch_check_stack(&this_size, &max_stack_trace, &max_stack_size);
>
> Where a weak function can be defined to return nothing. But the arch
> can check which stack the "this_size" variable is on and run the
> stack tracer against that stack.
>
> Maybe we should have two stack traces, a stack_trace file and a
> stack_trace_irq ?
>
> Because, some archs, like x86_64 have different size stacks. The
> thread stack is 8K where as the IRQ stack is 4K. We may want to see
> which IRQ stack call is the worst, and not compare it to the thread
> stack call.

... and on 64-bit x86 the IRQ stacks are 16K, and some of the IST
exception stacks have different sizes as well.

Ingo


\
 
 \ /
  Last update: 2008-11-18 16:05    [W:0.206 / U:0.064 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site