1. 06 11月, 2008 3 次提交
    • S
      ftrace: soft tracing stop and start · 0f048701
      Steven Rostedt 提交于
      Impact: add way to quickly start stop tracing from the kernel
      
      This patch adds a soft stop and start to the trace. This simply
      disables function tracing via the ftrace_disabled flag, and
      disables the trace buffers to prevent recording. The tracing
      code may still be executed, but the trace will not be recorded.
      Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      0f048701
    • S
      ftrace: add quick function trace stop · 60a7ecf4
      Steven Rostedt 提交于
      Impact: quick start and stop of function tracer
      
      This patch adds a way to disable the function tracer quickly without
      the need to run kstop_machine. It adds a new variable called
      function_trace_stop which will stop the calls to functions from mcount
      when set.  This is just an on/off switch and does not handle recursion
      like preempt_disable().
      
      It's main purpose is to help other tracers/debuggers start and stop tracing
      fuctions without the need to call kstop_machine.
      
      The config option HAVE_FUNCTION_TRACE_MCOUNT_TEST is added for archs
      that implement the testing of the function_trace_stop in the mcount
      arch dependent code. Otherwise, the test is done in the C code.
      
      x86 is the only arch at the moment that supports this.
      Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      60a7ecf4
    • I
      Merge branch 'tracing/fastboot' into tracing/ftrace · 79c81d22
      Ingo Molnar 提交于
      79c81d22
  2. 05 11月, 2008 6 次提交
  3. 04 11月, 2008 5 次提交
    • P
      ftrace: sysctl typo · 3299b4dd
      Peter Zijlstra 提交于
      Impact: fix sysctl name typo
      
      Steve must have needed more coffee ;-)
      Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      3299b4dd
    • P
      ftrace: sysrq-z to dump the buffers · 69f698ad
      Peter Zijlstra 提交于
      Impact: add SysRq-z support to dump trace buffers
      
      Allows one to force an ftrace dump from sysrq
      Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
      Acked-by: NSteven Rostedt <srostedt@redhat.com>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      69f698ad
    • S
      ftrace: function tracer with irqs disabled · b2a866f9
      Steven Rostedt 提交于
      Impact: disable interrupts during trace entry creation (as opposed to preempt)
      
      To help with performance, I set the ftracer to not disable interrupts,
      and only to disable preemption. If an interrupt occurred, it would not
      be traced, because the function tracer protects itself from recursion.
      This may be faster, but the trace output might miss some traces.
      
      This patch makes the fuction trace disable interrupts, but it also
      adds a runtime feature to disable preemption instead. It does this by
      having two different tracer functions. When the function tracer is
      enabled, it will check to see which version is requested (irqs disabled
      or preemption disabled). Then it will use the corresponding function
      as the tracer.
      
      Irq disabling is the default behaviour, but if the user wants better
      performance, with the chance of missing traces, then they can choose
      the preempt disabled version.
      
      Running hackbench 3 times with the irqs disabled and 3 times with
      the preempt disabled function tracer yielded:
      
      tracing type       times            entries recorded
      ------------      --------          ----------------
      irq disabled      43.393            166433066
                        43.282            166172618
                        43.298            166256704
      
      preempt disabled  38.969            159871710
                        38.943            159972935
                        39.325            161056510
      
      Average:
      
         irqs disabled:  43.324           166287462
      preempt disabled:  39.079           160300385
      
       preempt is 10.8 percent faster than irqs disabled.
      
      I wrote a patch to count function trace recursion and reran hackbench.
      
      With irq disabled: 1,150 times the function tracer did not trace due to
        recursion.
      with preempt disabled: 5,117,718 times.
      
      The thousand times with irq disabled could be due to NMIs, or simply a case
      where it called a function that was not protected by notrace.
      
      But we also see that a large amount of the trace is lost with the
      preempt version.
      Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Steven Rostedt <srostedt@redhat.com>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      b2a866f9
    • S
      ftrace: insert in the ftrace_preempt_disable()/enable() functions · 182e9f5f
      Steven Rostedt 提交于
      Impact: use new, consolidated APIs in ftrace plugins
      
      This patch replaces the schedule safe preempt disable code with the
      ftrace_preempt_disable() and ftrace_preempt_enable() safe functions.
      Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      182e9f5f
    • S
      ftrace: introduce ftrace_preempt_disable()/enable() · 8f0a056f
      Steven Rostedt 提交于
      Impact: add new ftrace-plugin internal APIs
      
      Parts of the tracer needs to be careful about schedule recursion.
      If the NEED_RESCHED flag is set, a preempt_enable will call schedule.
      Inside the schedule function, the NEED_RESCHED flag is cleared.
      
      The problem arises when a trace happens in the schedule function but before
      NEED_RESCHED is cleared. The race is as follows:
      
      schedule()
        >> tracer called
      
          trace_function()
             preempt_disable()
             [ record trace ]
             preempt_enable()  <<- here's the issue.
      
               [check NEED_RESCHED]
                schedule()
                [ Repeat the above, over and over again ]
      
      The naive approach is simply to use preempt_enable_no_schedule instead.
      The problem with that approach is that, although we solve the schedule
      recursion issue, we now might lose a preemption check when not in the
      schedule function.
      
        trace_function()
          preempt_disable()
          [ record trace ]
          [Interrupt comes in and sets NEED_RESCHED]
          preempt_enable_no_resched()
          [continue without scheduling]
      
      The way ftrace handles this problem is with the following approach:
      
      	int resched;
      
      	resched = need_resched();
      	preempt_disable_notrace();
      	[record trace]
      	if (resched)
      		preempt_enable_no_sched_notrace();
      	else
      		preempt_enable_notrace();
      
      This may seem like the opposite of what we want. If resched is set
      then we call the "no_sched" version??  The reason we do this is because
      if NEED_RESCHED is set before we disable preemption, there's two reasons
      for that:
      
        1) we are in an atomic code path
        2) we are already on our way to the schedule function, and maybe even
           in the schedule function, but have yet to clear the flag.
      
      Both the above cases we do not want to schedule.
      
      This solution has already been implemented within the ftrace infrastructure.
      But the problem is that it has been implemented several times. This patch
      encapsulates this code to two nice functions.
      
        resched = ftrace_preempt_disable();
        [ record trace]
        ftrace_preempt_enable(resched);
      
      This way the tracers do not need to worry about getting it right.
      Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      8f0a056f
  4. 03 11月, 2008 17 次提交
  5. 02 11月, 2008 9 次提交