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ps: stop using AT_CLKTCK, there are more standard ways

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function                                             old     new   delta
ps_main                                              537     558     +21
func_time                                             66      59      -7
get_kernel_HZ                                        102       -    -102
------------------------------------------------------------------------------
(add/remove: 0/1 grow/shrink: 1/1 up/down: 21/-109)           Total: -88 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2017-08-10 14:10:56 +02:00
parent 5da5365d3c
commit 1fd8e66203
1 changed files with 10 additions and 95 deletions
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105
procps/ps.c
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@ -145,12 +145,6 @@ static unsigned long get_uptime(void)
#endif
#if ENABLE_DESKTOP
#include <sys/times.h> /* for times() */
#ifndef AT_CLKTCK
# define AT_CLKTCK 17
#endif
/* TODO:
* http://pubs.opengroup.org/onlinepubs/9699919799/utilities/ps.html
* specifies (for XSI-conformant systems) following default columns
@ -187,7 +181,9 @@ struct globals {
char *buffer;
unsigned terminal_width;
#if ENABLE_FEATURE_PS_TIME
# if ENABLE_FEATURE_PS_UNUSUAL_SYSTEMS || !defined(__linux__)
unsigned kernel_HZ;
# endif
unsigned long seconds_since_boot;
#endif
} FIX_ALIASING;
@ -198,92 +194,15 @@ struct globals {
#define need_flags (G.need_flags )
#define buffer (G.buffer )
#define terminal_width (G.terminal_width )
#define kernel_HZ (G.kernel_HZ )
#define INIT_G() do { setup_common_bufsiz(); } while (0)
#if ENABLE_FEATURE_PS_TIME
/* for ELF executables, notes are pushed before environment and args */
/* try "LD_SHOW_AUXV=1 /bin/true" */
static uintptr_t find_elf_note(uintptr_t findme)
{
uintptr_t *ep = (uintptr_t *) environ;
while (*ep++)
continue;
while (*ep) {
if (ep[0] == findme) {
return ep[1];
}
ep += 2;
}
return -1;
}
# if ENABLE_FEATURE_PS_UNUSUAL_SYSTEMS
static unsigned get_HZ_by_waiting(void)
{
struct timeval tv1, tv2;
unsigned t1, t2, r, hz;
unsigned cnt = cnt; /* for compiler */
int diff;
r = 0;
/* Wait for times() to reach new tick */
t1 = times(NULL);
do {
t2 = times(NULL);
} while (t2 == t1);
gettimeofday(&tv2, NULL);
do {
t1 = t2;
tv1.tv_usec = tv2.tv_usec;
/* Wait exactly one times() tick */
do {
t2 = times(NULL);
} while (t2 == t1);
gettimeofday(&tv2, NULL);
/* Calculate ticks per sec, rounding up to even */
diff = tv2.tv_usec - tv1.tv_usec;
if (diff <= 0) diff += 1000000;
hz = 1000000u / (unsigned)diff;
hz = (hz+1) & ~1;
/* Count how many same hz values we saw */
if (r != hz) {
r = hz;
cnt = 0;
}
cnt++;
} while (cnt < 3); /* exit if saw 3 same values */
return r;
}
# if ENABLE_FEATURE_PS_UNUSUAL_SYSTEMS || !defined(__linux__)
# define get_kernel_HZ() (G.kernel_HZ)
# else
static inline unsigned get_HZ_by_waiting(void)
{
/* Better method? */
return 100;
}
/* non-ancient Linux standardized on 100 for "times" freq */
# define get_kernel_HZ() ((unsigned)100)
# endif
static unsigned get_kernel_HZ(void)
{
if (kernel_HZ)
return kernel_HZ;
/* Works for ELF only, Linux 2.4.0+ */
kernel_HZ = find_elf_note(AT_CLKTCK);
if (kernel_HZ == (unsigned)-1)
kernel_HZ = get_HZ_by_waiting();
G.seconds_since_boot = get_uptime();
return kernel_HZ;
}
#endif
/* Print value to buf, max size+1 chars (including trailing '\0') */
@ -375,26 +294,21 @@ static void func_tty(char *buf, int size, const procps_status_t *ps)
}
#if ENABLE_FEATURE_PS_ADDITIONAL_COLUMNS
static void func_rgroup(char *buf, int size, const procps_status_t *ps)
{
safe_strncpy(buf, get_cached_groupname(ps->rgid), size+1);
}
static void func_ruser(char *buf, int size, const procps_status_t *ps)
{
safe_strncpy(buf, get_cached_username(ps->ruid), size+1);
}
static void func_nice(char *buf, int size, const procps_status_t *ps)
{
sprintf(buf, "%*d", size, ps->niceness);
}
#endif
#if ENABLE_FEATURE_PS_TIME
static void func_etime(char *buf, int size, const procps_status_t *ps)
{
/* elapsed time [[dd-]hh:]mm:ss; here only mm:ss */
@ -402,13 +316,11 @@ static void func_etime(char *buf, int size, const procps_status_t *ps)
unsigned ss;
mm = ps->start_time / get_kernel_HZ();
/* must be after get_kernel_HZ()! */
mm = G.seconds_since_boot - mm;
ss = mm % 60;
mm /= 60;
snprintf(buf, size+1, "%3lu:%02u", mm, ss);
}
static void func_time(char *buf, int size, const procps_status_t *ps)
{
/* cumulative time [[dd-]hh:]mm:ss; here only mm:ss */
@ -420,7 +332,6 @@ static void func_time(char *buf, int size, const procps_status_t *ps)
mm /= 60;
snprintf(buf, size+1, "%3lu:%02u", mm, ss);
}
#endif
#if ENABLE_SELINUX
@ -627,6 +538,10 @@ int ps_main(int argc UNUSED_PARAM, char **argv)
};
INIT_G();
G.seconds_since_boot = get_uptime();
#if ENABLE_FEATURE_PS_TIME && (ENABLE_FEATURE_PS_UNUSUAL_SYSTEMS || !defined(__linux__))
G.kernel_HZ = bb_clk_tck(); /* this is sysconf(_SC_CLK_TCK) */
#endif
// POSIX:
// -a Write information for all processes associated with terminals