[ping2][PATCH v2] Add systemtap markers to math function slow paths

[Siddhesh Poyarekar <siddhesh at redhat dot com>]

Ping!

On Fri, Oct 04, 2013 at 11:21:26AM +0530, Siddhesh Poyarekar wrote:
> Ping!
> 
> On Tue, Sep 17, 2013 at 11:48:18AM +0530, Siddhesh Poyarekar wrote:
> > Hi.
> > 
> > Here is take two of the probes patch with documentation added to
> > probes.texi that Alexandre Oliva proposed[1] to add to the glibc
> > manual.  These probes are hit only in the slow paths of the respective
> > functions and are a good aid for developers to see if their
> > application uses any inputs that may be resulting in these slow paths
> > being invoked.
> > 
> > Regards,
> > Siddhesh
> > 
> > 2013-09-11  Siddhesh Poyarekar  <siddhesh@redhat.com>
> > 	    Jeff Law  <law@redhat.com>
> > 
> > 	* sysdeps/ieee754/dbl-64/e_atan2.c: Include stap-probe.h.
> > 	(atan2Mp): Add systemtap probe marker.
> > 	* sysdeps/ieee754/dbl-64/e_log.c: include stap-probe.h.
> > 	(__ieee754_log): Add systemtap probe marker.
> > 	* sysdeps/ieee754/dbl-64/s_atan.c: Include stap-probe.h.
> > 	(atanMp): Add systemtap probe marker.
> > 	* sysdeps/ieee754/dbl-64/s_tan.c: Include stap-probe.h.
> > 	(tanMp): Add systemtap probe marker.
> > 	* sysdeps/ieee754/dbl-64/slowexp.c: Include stap-probe.h.
> > 	(__slowexp): Add systemtap probe marker.
> > 	* sysdeps/ieee754/dbl-64/slowpow.c: Include stap-probe.h.
> > 	(__slowpow): Add systemtap probe marker.
> > 	* manual/probes.texi: Document probes.
> > 
> > diff --git a/manual/probes.texi b/manual/probes.texi
> > index 650bea7..7b5f192 100644
> > --- a/manual/probes.texi
> > +++ b/manual/probes.texi
> > @@ -16,6 +16,7 @@ arguments.
> >  
> >  @menu
> >  * Memory Allocation Probes::  Probes in the memory allocation subsystem
> > +* Mathematical Function Probes::  Probes in mathematical functions
> >  @end menu
> >  
> >  @node Memory Allocation Probes
> > @@ -249,3 +250,100 @@ This probe is hit when function @code{free} decides to adjust the
> >  dynamic brk/mmap thresholds.  Argument @var{$arg1} and @var{$arg2} are
> >  the adjusted mmap and trim thresholds, respectively.
> >  @end deftp
> > +
> > +@node Mathematical Function Probes
> > +@section Mathematical Function Probes
> > +
> > +Some mathematical functions fall back to multiple precision arithmetic for
> > +some inputs to get last bit precision for their return values.  This multiple
> > +precision fallback is much slower than the default algorithms and may have a
> > +significant impact on application performance.  The systemtap probe markers
> > +described in this section may help you determine if your application calls
> > +mathematical functions with inputs that may result in multiple-precision
> > +arithmetic.
> > +
> > +Unless explicitly mentioned otherwise, a precision of 1 implies 24 bits of
> > +precision in the mantissa of the multiple precision number.  Hence, a precision
> > +level of 32 implies 768 bits of precision in the mantissa.
> > +
> > +@deftp Probe slowexp_p6 (double @var{$arg1}, double @var{$arg2})
> > +This probe is hit when the @code{exp} function is called with an input that
> > +results in multiple precision computation with precision 6. Argument
> > +@var{$arg1} is the input value and @var{$arg2} is the computed output.
> > +@end deftp
> > +
> > +@deftp Probe slowexp_p32 (double @var{$arg1}, double @var{$arg2})
> > +This probe is hit when the @code{exp} function is called with an input that
> > +results in multiple precision computation with precision 32. Argument
> > +@var{$arg1} is the input value and @var{$arg2} is the computed output.
> > +@end deftp
> > +
> > +@deftp Probe slowpow_p10 (double @var{$arg1}, double @var{$arg2}, double @var{$arg3}, double @var{$arg4})
> > +This probe is hit when the @code{pow} function is called with inputs that
> > +result in multiple precision computation with precision 10. Arguments
> > +@var{$arg1} and @var{$arg2} are the input values, @code{$arg3} is the value
> > +computed in the fast phase of the algorithm and @code{$arg4} is the final
> > +accurate value.
> > +@end deftp
> > +
> > +@deftp Probe slowpow_p32 (double @var{$arg1}, double @var{$arg2}, double @var{$arg3}, double @var{$arg4})
> > +This probe is hit when the @code{pow} function is called with an input that
> > +results in multiple precision computation with precision 32. Arguments
> > +@var{$arg1} and @var{$arg2} are the input values, @code{$arg3} is the value
> > +computed in the fast phase of the algorithm and @code{$arg4} is the final
> > +accurate value.
> > +@end deftp
> > +
> > +@deftp Probe slowlog (int @var{$arg1}, double @var{$arg2}, double @var{$arg3})
> > +This probe is hit when the @code{log} function is called with an input that
> > +results in multiple precision computation.  Argument @var{$arg1} is the
> > +precision with which the computation succeeded.  Argument @var{$arg2} is the
> > +input and @var{$arg3} is the computed output.
> > +@end deftp
> > +
> > +@deftp Probe slowlog_inexact (int @var{$arg1}, double @var{$arg2}, double @var{$arg3})
> > +This probe is hit when the @code{log} function is called with an input that
> > +results in multiple precision computation and none of the multiple precision
> > +computations result in an accurate result.  Argument @var{$arg1} is the maximum
> > +precision  with which computations were performed.  Argument @var{$arg2} is the
> > +input and @var{$arg3} is the computed output.
> > +@end deftp
> > +
> > +@deftp Probe slowatan2 (int @var{$arg1}, double @var{$arg2}, double @var{$arg3}, double @var{$arg4})
> > +This probe is hit when the @code{atan2} function is called with an input that
> > +results in multiple precision computation.  Argument @var{$arg1} is the
> > +precision with which computation succeeded.  Arguments @var{$arg2} and
> > +@var{$arg3} are inputs to the @code{atan2} function and @var{$arg4} is the
> > +computed result.
> > +@end deftp
> > +
> > +@deftp Probe slowatan2_inexact (int @var{$arg1}, double @var{$arg2}, double @var{$arg3}, double @var{$arg4})
> > +This probe is hit when the @code{atan} function is called with an input that
> > +results in multiple precision computation and none of the multiple precision
> > +computations result in an accurate result.  Argument @var{$arg1} is the maximum
> > +precision  with which computations were performed.  Arguments @var{$arg2} and
> > +@var{$arg3} are inputs to the @code{atan2} function and @var{$arg4} is the
> > +computed result.
> > +@end deftp
> > +
> > +@deftp Probe slowatan (int @var{$arg1}, double @var{$arg2}, double @var{$arg3})
> > +This probe is hit when the @code{atan} function is called with an input that
> > +results in multiple precision computation.  Argument @var{$arg1} is the
> > +precision with which computation succeeded.  Argument @var{$arg2} is the
> > +input to the @code{atan} function and @var{$arg3} is the computed result.
> > +@end deftp
> > +
> > +@deftp Probe slowatan_inexact (int @var{$arg1}, double @var{$arg2}, double @var{$arg3})
> > +This probe is hit when the @code{atan} function is called with an input that
> > +results in multiple precision computation and none of the multiple precision
> > +computations result in an accurate result.  Argument @var{$arg1} is the maximum
> > +precision  with which computations were performed.  Argument @var{$arg2} is the
> > +input to the @code{atan} function and @var{$arg3} is the computed result.
> > +@end deftp
> > +
> > +@deftp Probe slowtan (double @var{$arg1}, double @var{$arg2})
> > +This probe is hit when the @code{tan} function is called with an input that
> > +results in multiple precision computation with precision 32.  Argument
> > +@var{$arg1} is the input to the function and @var{$arg2} is the computed
> > +result.
> > +@end deftp
> > diff --git a/sysdeps/ieee754/dbl-64/e_atan2.c b/sysdeps/ieee754/dbl-64/e_atan2.c
> > index 4ebe9c0..4075622 100644
> > --- a/sysdeps/ieee754/dbl-64/e_atan2.c
> > +++ b/sysdeps/ieee754/dbl-64/e_atan2.c
> > @@ -42,6 +42,7 @@
> >  #include "uatan.tbl"
> >  #include "atnat2.h"
> >  #include <math_private.h>
> > +#include <stap-probe.h>
> >  
> >  #ifndef SECTION
> >  # define SECTION
> > @@ -597,7 +598,11 @@ atan2Mp (double x, double y, const int pr[])
> >        __mp_dbl (&mpz1, &z1, p);
> >        __mp_dbl (&mpz2, &z2, p);
> >        if (z1 == z2)
> > -	return z1;
> > +	{
> > +	  LIBC_PROBE (slowatan2, 4, &p, &x, &y, &z1);
> > +	  return z1;
> > +	}
> >      }
> > +  LIBC_PROBE (slowatan2_inexact, 4, &p, &x, &y, &z1);
> >    return z1;			/*if impossible to do exact computing */
> >  }
> > diff --git a/sysdeps/ieee754/dbl-64/e_log.c b/sysdeps/ieee754/dbl-64/e_log.c
> > index f9300f9..17ab75a 100644
> > --- a/sysdeps/ieee754/dbl-64/e_log.c
> > +++ b/sysdeps/ieee754/dbl-64/e_log.c
> > @@ -39,6 +39,7 @@
> >  #include "mpa.h"
> >  #include "MathLib.h"
> >  #include <math_private.h>
> > +#include <stap-probe.h>
> >  
> >  #ifndef SECTION
> >  # define SECTION
> > @@ -242,8 +243,12 @@ stage_n:
> >        __mp_dbl (&mpy1, &y1, p);
> >        __mp_dbl (&mpy2, &y2, p);
> >        if (y1 == y2)
> > -	return y1;
> > +	{
> > +	  LIBC_PROBE (slowlog, 3, &p, &x, &y1);
> > +	  return y1;
> > +	}
> >      }
> > +  LIBC_PROBE (slowlog_inexact, 3, &p, &x, &y1);
> >    return y1;
> >  }
> >  
> > diff --git a/sysdeps/ieee754/dbl-64/s_atan.c b/sysdeps/ieee754/dbl-64/s_atan.c
> > index 7b6c83f..35ab5c1 100644
> > --- a/sysdeps/ieee754/dbl-64/s_atan.c
> > +++ b/sysdeps/ieee754/dbl-64/s_atan.c
> > @@ -42,6 +42,7 @@
> >  #include "uatan.tbl"
> >  #include "atnat.h"
> >  #include <math.h>
> > +#include <stap-probe.h>
> >  
> >  void __mpatan (mp_no *, mp_no *, int);	/* see definition in mpatan.c */
> >  static double atanMp (double, const int[]);
> > @@ -306,8 +307,12 @@ atanMp (double x, const int pr[])
> >        __mp_dbl (&mpy1, &y1, p);
> >        __mp_dbl (&mpy2, &y2, p);
> >        if (y1 == y2)
> > -	return y1;
> > +	{
> > +	  LIBC_PROBE (slowatan, 3, &p, &x, &y1);
> > +	  return y1;
> > +	}
> >      }
> > +  LIBC_PROBE (slowatan_inexact, 3, &p, &x, &y1);
> >    return y1;			/*if impossible to do exact computing */
> >  }
> >  
> > diff --git a/sysdeps/ieee754/dbl-64/s_tan.c b/sysdeps/ieee754/dbl-64/s_tan.c
> > index 54f863e..cc0dbbb 100644
> > --- a/sysdeps/ieee754/dbl-64/s_tan.c
> > +++ b/sysdeps/ieee754/dbl-64/s_tan.c
> > @@ -41,6 +41,7 @@
> >  #include <math.h>
> >  #include <math_private.h>
> >  #include <fenv.h>
> > +#include <stap-probe.h>
> >  
> >  #ifndef SECTION
> >  # define SECTION
> > @@ -838,6 +839,7 @@ tanMp (double x)
> >    p = 32;
> >    __mptan (x, &mpy, p);
> >    __mp_dbl (&mpy, &y, p);
> > +  LIBC_PROBE (slowtan, 2, &x, &y);
> >    return y;
> >  }
> >  
> > diff --git a/sysdeps/ieee754/dbl-64/slowexp.c b/sysdeps/ieee754/dbl-64/slowexp.c
> > index 8f353f6..525224f 100644
> > --- a/sysdeps/ieee754/dbl-64/slowexp.c
> > +++ b/sysdeps/ieee754/dbl-64/slowexp.c
> > @@ -29,6 +29,8 @@
> >  /**************************************************************************/
> >  #include <math_private.h>
> >  
> > +#include <stap-probe.h>
> > +
> >  #ifndef USE_LONG_DOUBLE_FOR_MP
> >  # include "mpa.h"
> >  void __mpexp (mp_no *x, mp_no *y, int p);
> > @@ -60,13 +62,22 @@ __slowexp (double x)
> >    __mp_dbl (&mpw, &w, p);
> >    __mp_dbl (&mpz, &z, p);
> >    if (w == z)
> > -    return w;
> > +    {
> > +      /* Track how often we get to the slow exp code plus
> > +	 its input/output values.  */
> > +      LIBC_PROBE (slowexp_p6, 2, &x, &w);
> > +      return w;
> > +    }
> >    else
> >      {
> >        p = 32;
> >        __dbl_mp (x, &mpx, p);
> >        __mpexp (&mpx, &mpy, p);
> >        __mp_dbl (&mpy, &res, p);
> > +
> > +      /* Track how often we get to the uber-slow exp code plus
> > +	 its input/output values.  */
> > +      LIBC_PROBE (slowexp_p32, 2, &x, &res);
> >        return res;
> >      }
> >  #else
> > diff --git a/sysdeps/ieee754/dbl-64/slowpow.c b/sysdeps/ieee754/dbl-64/slowpow.c
> > index a379728..d200c39 100644
> > --- a/sysdeps/ieee754/dbl-64/slowpow.c
> > +++ b/sysdeps/ieee754/dbl-64/slowpow.c
> > @@ -34,6 +34,8 @@
> >  #include "mpa.h"
> >  #include <math_private.h>
> >  
> > +#include <stap-probe.h>
> > +
> >  #ifndef SECTION
> >  # define SECTION
> >  #endif
> > @@ -97,7 +99,12 @@ __slowpow (double x, double y, double z)
> >    __sub (&mpp, &eps, &mpr1, p);
> >    __mp_dbl (&mpr1, &res1, p);
> >    if (res == res1)
> > -    return res;
> > +    {
> > +      /* Track how often we get to the slow pow code plus
> > +	 its input/output values.  */
> > +      LIBC_PROBE (slowpow_p10, 4, &x, &y, &z, &res);
> > +      return res;
> > +    }
> >  
> >    /* If we don't, then we repeat using a higher precision.  768 bits of
> >       precision ought to be enough for anybody.  */
> > @@ -109,5 +116,10 @@ __slowpow (double x, double y, double z)
> >    __mul (&mpy, &mpz, &mpw, p);
> >    __mpexp (&mpw, &mpp, p);
> >    __mp_dbl (&mpp, &res, p);
> > +
> > +  /* Track how often we get to the uber-slow pow code plus
> > +     its input/output values.  */
> > +  LIBC_PROBE (slowpow_p32, 4, &x, &y, &z, &res);
> > +
> >    return res;
> >  }