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[svn] Better selection of POSIX clocks.

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hniksic 2005-04-08 11:19:20 -07:00
parent ab05800310
commit 14a2d25b2e
4 changed files with 268 additions and 199 deletions
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17
src/ChangeLog
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@ -1,3 +1,20 @@
2005-04-08 Hrvoje Niksic <hniksic@xemacs.org>
* ptimer.c (posix_init): Be smarter about choosing clocks. In
decreasing order of preference, use CLOCK_MONOTONIC,
CLOCK_HIGHRES, and CLOCK_REALTIME.
(ptimer_allocate): Removed.
* ptimer.c: Refactor the code by cleanly separating the
architecture-dependent code from the architecture-independent
code.
2005-04-08 Hrvoje Niksic <hniksic@xemacs.org>
* ptimer.c (ptimer_init): Explicitly check that
_POSIX_MONOTONIC_CLOCK is *both* defined and >=0. (Undefined
symbols are >=0.)
2005-04-08 Hrvoje Niksic <hniksic@xemacs.org>
* ptimer.c (ptimer_diff): Fix typo affecting Windows build.

441
src/ptimer.c
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@ -73,13 +73,8 @@ extern int errno;
#endif
/* Depending on the OS and availability of gettimeofday(), one and
only one of PTIMER_WINDOWS, PTIMER_GETTIMEOFDAY, or PTIMER_TIME will
be defined.
Virtually all modern Unix systems will define PTIMER_GETTIMEOFDAY;
Windows will use PTIMER_WINDOWS. PTIMER_TIME is a catch-all method
for non-Windows systems without gettimeofday, such as DOS or really
old Unix-like systems. */
only one of PTIMER_POSIX, PTIMER_GETTIMEOFDAY, PTIMER_WINDOWS, or
PTIMER_TIME will be defined. */
#undef PTIMER_POSIX
#undef PTIMER_GETTIMEOFDAY
@ -100,26 +95,247 @@ extern int errno;
# endif
#endif
/* The type ptimer_system_time holds system time. */
#ifdef PTIMER_POSIX
/* Elapsed time measurement using POSIX timers: system time is held in
struct timespec, time is retrieved using clock_gettime, and
resolution using clock_getres.
This method is used on Unix systems that implement POSIX
timers. */
typedef struct timespec ptimer_system_time;
#define IMPL_init posix_init
#define IMPL_measure posix_measure
#define IMPL_diff posix_diff
#define IMPL_resolution posix_resolution
/* clock_id to use for POSIX clocks. This tries to use
CLOCK_MONOTONIC where available, CLOCK_REALTIME otherwise. */
static int posix_clock_id;
/* Resolution of the clock, in milliseconds. */
static double posix_millisec_resolution;
/* Decide which clock_id to use. */
static void
posix_init (void)
{
/* List of clocks we want to support: some systems support monotonic
clocks, Solaris has "high resolution" clock (sometimes
unavailable except to superuser), and all should support the
real-time clock. */
#define NO_SYSCONF_CHECK -1
static const struct {
int id;
int sysconf_name;
} clocks[] = {
#if defined(_POSIX_MONOTONIC_CLOCK) && _POSIX_MONOTONIC_CLOCK >= 0
{ CLOCK_MONOTONIC, _SC_MONOTONIC_CLOCK },
#endif
#ifdef CLOCK_HIGHRES
{ CLOCK_HIGHRES, NO_SYSCONF_CHECK },
#endif
{ CLOCK_REALTIME, NO_SYSCONF_CHECK },
};
int i;
/* Determine the clock we can use. For a clock to be usable, it
must be confirmed with sysconf (where applicable) and with
clock_getres. If no clock is found, CLOCK_REALTIME is used. */
for (i = 0; i < countof (clocks); i++)
{
struct timespec r;
if (clocks[i].sysconf_name != NO_SYSCONF_CHECK)
if (sysconf (clocks[i].sysconf_name) < 0)
continue; /* sysconf claims this clock is unavailable */
if (clock_getres (clocks[i].id, &r) < 0)
continue; /* clock_getres doesn't work for this clock */
posix_clock_id = clocks[i].id;
posix_millisec_resolution = r.tv_sec * 1000.0 + r.tv_nsec / 1000000.0;
/* Guard against broken clock_getres returning nonsensical
values. */
if (posix_millisec_resolution == 0)
posix_millisec_resolution = 1;
break;
}
if (i == countof (clocks))
{
/* If no clock was found, it means that clock_getres failed for
the realtime clock. */
logprintf (LOG_NOTQUIET, _("Cannot get REALTIME clock frequency: %s\n"),
strerror (errno));
/* Use CLOCK_REALTIME, but invent a plausible resolution. */
posix_clock_id = CLOCK_REALTIME;
posix_millisec_resolution = 1;
}
}
static inline void
posix_measure (ptimer_system_time *pst)
{
clock_gettime (posix_clock_id, pst);
}
static inline double
posix_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
{
return ((pst1->tv_sec - pst2->tv_sec) * 1000.0
+ (pst1->tv_nsec - pst2->tv_nsec) / 1000000.0);
}
static inline double
posix_resolution (void)
{
return posix_millisec_resolution;
}
#endif /* PTIMER_POSIX */
#ifdef PTIMER_GETTIMEOFDAY
/* Elapsed time measurement using gettimeofday: system time is held in
struct timeval, retrieved using gettimeofday, and resolution is
unknown.
This method is used Unix systems without POSIX timers. */
typedef struct timeval ptimer_system_time;
#endif
#define IMPL_measure gettimeofday_measure
#define IMPL_diff gettimeofday_diff
#define IMPL_resolution gettimeofday_resolution
static inline void
gettimeofday_measure (ptimer_system_time *pst)
{
gettimeofday (pst, NULL);
}
static inline double
gettimeofday_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
{
return ((pst1->tv_sec - pst2->tv_sec) * 1000.0
+ (pst1->tv_usec - pst2->tv_usec) / 1000.0);
}
static inline double
gettimeofday_resolution (void)
{
/* Granularity of gettimeofday varies wildly between architectures.
However, it appears that on modern machines it tends to be better
than 1ms. Assume 100 usecs. */
return 0.1;
}
#endif /* PTIMER_GETTIMEOFDAY */
#ifdef PTIMER_TIME
/* Elapsed time measurement using the time(2) call: system time is
held in time_t, retrieved using time, and resolution is 1 second.
This method is a catch-all for non-Windows systems without
gettimeofday -- e.g. DOS or really old or non-standard Unix
systems. */
typedef time_t ptimer_system_time;
#endif
#define IMPL_measure time_measure
#define IMPL_diff time_diff
#define IMPL_resolution time_resolution
static inline void
time_measure (ptimer_system_time *pst)
{
time (pst);
}
static inline double
time_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
{
return 1000.0 * (*pst1 - *pst2);
}
static inline double
time_resolution (void)
{
return 1;
}
#endif /* PTIMER_TIME */
#ifdef PTIMER_WINDOWS
/* Elapsed time measurement on Windows: where high-resolution timers
are available, time is stored in a LARGE_INTEGER and retrieved
using QueryPerformanceCounter. Otherwise, it is stored in a DWORD
and retrieved using GetTickCount.
This method is used on Windows. */
typedef union {
DWORD lores; /* In case GetTickCount is used */
LARGE_INTEGER hires; /* In case high-resolution timer is used */
} ptimer_system_time;
#endif
#define IMPL_init windows_init
#define IMPL_measure windows_measure
#define IMPL_diff windows_diff
#define IMPL_resolution windows_resolution
/* Whether high-resolution timers are used. Set by ptimer_initialize_once
the first time ptimer_new is called. */
static int windows_hires_timers;
/* Frequency of high-resolution timers -- number of updates per
millisecond. Calculated the first time ptimer_new is called
provided that high-resolution timers are available. */
static double windows_hires_msfreq;
static void
windows_init (void)
{
LARGE_INTEGER freq;
freq.QuadPart = 0;
QueryPerformanceFrequency (&freq);
if (freq.QuadPart != 0)
{
windows_hires_timers = 1;
windows_hires_msfreq = (double) freq.QuadPart / 1000.0;
}
}
static inline void
windows_measure (ptimer_system_time *pst)
{
if (windows_hires_timers)
QueryPerformanceCounter (&pst->hires);
else
/* Where hires counters are not available, use GetTickCount rather
GetSystemTime, because it is unaffected by clock skew and
simpler to use. Note that overflows don't affect us because we
never use absolute values of the ticker, only the
differences. */
pst->lores = GetTickCount ();
}
static inline double
windows_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
{
if (windows_hires_timers)
return (pst1->hires.QuadPart - pst2->hires.QuadPart) / windows_hires_msfreq;
else
return pst1->lores - pst2->lores;
}
static double
windows_resolution (void)
{
if (windows_hires_timers)
return 1.0 / windows_hires_msfreq;
else
return 10; /* according to MSDN */
}
#endif /* PTIMER_WINDOWS */
/* The code below this point is independent of timer implementation. */
struct ptimer {
/* Whether the start time has been set. */
@ -134,108 +350,25 @@ struct ptimer {
double elapsed_last;
/* Approximately, the time elapsed between the true start of the
measurement and the time represented by START. */
measurement and the time represented by START. This is used for
adjustment when clock skew is detected. */
double elapsed_pre_start;
};
#ifdef PTIMER_WINDOWS
/* Whether high-resolution timers are used. Set by ptimer_initialize_once
the first time ptimer_allocate is called. */
static int windows_hires_timers;
/* Frequency of high-resolution timers -- number of updates per
millisecond. Calculated the first time ptimer_allocate is called
provided that high-resolution timers are available. */
static double windows_hires_msfreq;
/* The first time a timer is created, determine whether to use
high-resolution timers. */
static void
ptimer_init (void)
{
LARGE_INTEGER freq;
freq.QuadPart = 0;
QueryPerformanceFrequency (&freq);
if (freq.QuadPart != 0)
{
windows_hires_timers = 1;
windows_hires_msfreq = (double) freq.QuadPart / 1000.0;
}
}
#define PTIMER_INIT_DEFINED
#endif /* PTIMER_WINDOWS */
#ifdef PTIMER_POSIX
/* clock_id to use for POSIX clocks. This tries to use
CLOCK_MONOTONIC where available, CLOCK_REALTIME otherwise. */
static int posix_clock_id;
/* Resolution of the clock, in milliseconds. */
static double posix_resolution;
/* Check whether the monotonic clock is available, and retrieve POSIX
timer resolution. */
static void
ptimer_init (void)
{
struct timespec res;
#if _POSIX_MONOTONIC_CLOCK >= 0 /* -1 means not supported */
if (sysconf (_SC_MONOTONIC_CLOCK) > 0)
posix_clock_id = CLOCK_MONOTONIC;
else
#endif
posix_clock_id = CLOCK_REALTIME;
if (clock_getres (posix_clock_id, &res) < 0)
{
logprintf (LOG_NOTQUIET, _("Cannot read clock resolution: %s\n"),
strerror (errno));
/* Assume 1 ms resolution */
res.tv_sec = 0;
res.tv_nsec = 1000000;
}
posix_resolution = res.tv_sec * 1000.0 + res.tv_nsec / 1000000.0;
/* Guard against clock_getres reporting 0 resolution; after all, it
can be used for division. */
if (posix_resolution == 0)
posix_resolution = 1;
}
#define PTIMER_INIT_DEFINED
#endif
/* Allocate a timer. Calling ptimer_read on the timer will return
zero. It is not legal to call ptimer_measure with a freshly
allocated timer -- use ptimer_reset first. */
struct ptimer *
ptimer_allocate (void)
{
struct ptimer *wt;
#ifdef PTIMER_INIT_DEFINED
static int init_done;
if (!init_done)
{
init_done = 1;
ptimer_init ();
}
#endif
wt = xnew0 (struct ptimer);
return wt;
}
/* Allocate a new timer and reset it. Return the new timer. */
struct ptimer *
ptimer_new (void)
{
struct ptimer *wt = ptimer_allocate ();
struct ptimer *wt = xnew0 (struct ptimer);
#ifdef IMPL_init
static int init_done;
if (!init_done)
{
init_done = 1;
IMPL_init ();
}
#endif
ptimer_reset (wt);
return wt;
}
@ -249,39 +382,6 @@ ptimer_destroy (struct ptimer *wt)
xfree (wt);
}
/* Store system time to PST. */
static void
ptimer_sys_set (ptimer_system_time *pst)
{
#ifdef PTIMER_POSIX
clock_gettime (posix_clock_id, pst);
#endif
#ifdef PTIMER_GETTIMEOFDAY
gettimeofday (pst, NULL);
#endif
#ifdef PTIMER_TIME
time (pst);
#endif
#ifdef PTIMER_WINDOWS
if (windows_hires_timers)
{
QueryPerformanceCounter (&pst->hires);
}
else
{
/* Where hires counters are not available, use GetTickCount rather
GetSystemTime, because it is unaffected by clock skew and simpler
to use. Note that overflows don't affect us because we never use
absolute values of the ticker, only the differences. */
pst->lores = GetTickCount ();
}
#endif
}
/* Reset timer WT. This establishes the starting point from which
ptimer_read() will return the number of elapsed milliseconds.
It is allowed to reset a previously used timer. */
@ -290,37 +390,12 @@ void
ptimer_reset (struct ptimer *wt)
{
/* Set the start time to the current time. */
ptimer_sys_set (&wt->start);
IMPL_measure (&wt->start);
wt->elapsed_last = 0;
wt->elapsed_pre_start = 0;
wt->initialized = 1;
}
static double
ptimer_diff (ptimer_system_time *pst1, ptimer_system_time *pst2)
{
#ifdef PTIMER_POSIX
return ((pst1->tv_sec - pst2->tv_sec) * 1000.0
+ (pst1->tv_nsec - pst2->tv_nsec) / 1000000.0);
#endif
#ifdef PTIMER_GETTIMEOFDAY
return ((pst1->tv_sec - pst2->tv_sec) * 1000.0
+ (pst1->tv_usec - pst2->tv_usec) / 1000.0);
#endif
#ifdef PTIMER_TIME
return 1000 * (*pst1 - *pst2);
#endif
#ifdef WINDOWS
if (windows_hires_timers)
return (pst1->hires.QuadPart - pst2->hires.QuadPart) / windows_hires_msfreq;
else
return pst1->lores - pst2->lores;
#endif
}
/* Measure the elapsed time since timer creation/reset and return it
to the caller. The value remains stored for further reads by
ptimer_read.
@ -340,8 +415,8 @@ ptimer_measure (struct ptimer *wt)
assert (wt->initialized != 0);
ptimer_sys_set (&now);
elapsed = wt->elapsed_pre_start + ptimer_diff (&now, &wt->start);
IMPL_measure (&now);
elapsed = wt->elapsed_pre_start + IMPL_diff (&now, &wt->start);
/* Ideally we'd just return the difference between NOW and
wt->start. However, the system timer can be set back, and we
@ -356,8 +431,8 @@ ptimer_measure (struct ptimer *wt)
elapsed time and increment all future calculations by that
amount.
This cannot happen with Windows and CLOCK_MONOTONIC timers, but
the check is not expensive. */
This cannot happen with Windows and POSIX monotonic/highres
timers, but the check is not expensive. */
if (elapsed < wt->elapsed_last)
{
@ -379,34 +454,12 @@ ptimer_read (const struct ptimer *wt)
return wt->elapsed_last;
}
/* Return the assessed granularity of the timer implementation, in
/* Return the assessed resolution of the timer implementation, in
milliseconds. This is used by code that tries to substitute a
better value for timers that have returned zero. */
double
ptimer_granularity (void)
ptimer_resolution (void)
{
#ifdef PTIMER_POSIX
/* POSIX timers give us a way to measure granularity. */
assert (posix_resolution != 0);
return posix_resolution;
#endif
#ifdef PTIMER_GETTIMEOFDAY
/* Granularity of gettimeofday varies wildly between architectures.
However, it appears that on modern machines it tends to be better
than 1ms. Assume 100 usecs. */
return 0.1;
#endif
#ifdef PTIMER_TIME
return 1000;
#endif
#ifdef PTIMER_WINDOWS
if (windows_hires_timers)
return 1.0 / windows_hires_msfreq;
else
return 10; /* according to MSDN */
#endif
return IMPL_resolution ();
}

3
src/ptimer.h
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@ -33,7 +33,6 @@ so, delete this exception statement from your version. */
struct ptimer; /* forward declaration; all struct
members are private */
struct ptimer *ptimer_allocate PARAMS ((void));
struct ptimer *ptimer_new PARAMS ((void));
void ptimer_destroy PARAMS ((struct ptimer *));
@ -41,6 +40,6 @@ void ptimer_reset PARAMS ((struct ptimer *));
double ptimer_measure PARAMS ((struct ptimer *));
double ptimer_read PARAMS ((const struct ptimer *));
double ptimer_granularity PARAMS ((void));
double ptimer_resolution PARAMS ((void));
#endif /* PTIMER_H */

6
src/retr.c
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@ -534,10 +534,10 @@ calc_rate (wgint bytes, double msecs, int *units)
if (msecs == 0)
/* If elapsed time is exactly zero, it means we're under the
granularity of the timer. This can easily happen on systems
resolution of the timer. This can easily happen on systems
that use time() for the timer. Since the interval lies between
0 and the timer's granularity, assume half the granularity. */
msecs = ptimer_granularity () / 2.0;
0 and the timer's resolution, assume half the resolution. */
msecs = ptimer_resolution () / 2.0;
dlrate = 1000.0 * bytes / msecs;
if (dlrate < 1024.0)