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top,ps: reduce CPU usage in decimal conversion (optional)

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text    data     bss     dec     hex filename
 734651    3040   14416  752107   b79eb busybox_old
 734751    3040   14416  752207   b7a4f busybox_unstripped
This commit is contained in:
Denis Vlasenko 2007-06-19 13:46:24 +00:00
parent 08a61180ce
commit 3afac4ce06
2 changed files with 60 additions and 2 deletions
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7
libbb/Config.in
View File

@ -26,6 +26,13 @@ config MD5_SIZE_VS_SPEED
2 3.0 5088
3 (smallest) 5.1 4912
config FEATURE_FAST_TOP
bool "Faster /proc scanning code (+100 bytes)"
default n
help
This option makes top (and ps) ~20% faster (or 20% less CPU hungry),
but code size is slightly bigger.
config FEATURE_ETC_NETWORKS
bool "Support for /etc/networks"
default n

55
libbb/procps.c
View File

@ -107,6 +107,28 @@ void free_procps_scan(procps_status_t* sp)
free(sp);
}
#if ENABLE_FEATURE_FAST_TOP
/* We cut a lot of corners here for speed */
static unsigned long fast_strtoul_10(char *str, char **endptr)
{
char c;
unsigned long n = *str - '0';
while ((c = *++str) != ' ')
n = n*10 + (c - '0');
*endptr = str + 1; /* We skip trailing space! */
return n;
}
static char *skip_fields(char *str, int count)
{
do {
str = skip_non_whitespace(str); str++;
} while (--count);
return str;
}
#endif
void BUG_comm_size(void);
procps_status_t* procps_scan(procps_status_t* sp, int flags)
{
@ -160,7 +182,9 @@ procps_status_t* procps_scan(procps_status_t* sp, int flags)
if (flags & PSSCAN_STAT) {
char *cp;
#if !ENABLE_FEATURE_FAST_TOP
unsigned long vsz, rss;
#endif
int tty;
/* see proc(5) for some details on this */
@ -175,6 +199,8 @@ procps_status_t* procps_scan(procps_status_t* sp, int flags)
if (sizeof(sp->comm) < 16)
BUG_comm_size();
sscanf(buf, "%*s (%15c", sp->comm);
#if !ENABLE_FEATURE_FAST_TOP
n = sscanf(cp+2,
"%c %u " /* state, ppid */
"%u %u %d %*s " /* pgid, sid, tty, tpgid */
@ -197,6 +223,8 @@ procps_status_t* procps_scan(procps_status_t* sp, int flags)
&rss);
if (n != 10)
break;
sp->vsz = vsz >> 10; /* vsize is in bytes and we want kb */
sp->rss = rss >> 10;
sp->tty_str[0] = '?';
/* sp->tty_str[1] = '\0'; - done by memset */
@ -204,6 +232,31 @@ procps_status_t* procps_scan(procps_status_t* sp, int flags)
snprintf(sp->tty_str, sizeof(sp->tty_str), "%u,%u",
(tty >> 8) & 0xfff, /* major */
(tty & 0xff) | ((tty >> 12) & 0xfff00));
#else
/* This costs ~100 bytes more but makes top faster by 20%
* If you run 10000 processes, this may be important for you */
cp += 2;
sp->state[0] = *cp++; cp++;
sp->ppid = fast_strtoul_10(cp, &cp);
sp->pgid = fast_strtoul_10(cp, &cp);
sp->sid = fast_strtoul_10(cp, &cp);
sp->tty_str[0] = '?';
/* sp->tty_str[1] = '\0'; - done by memset */
tty = fast_strtoul_10(cp, &cp);
if (tty) /* tty field of "0" means "no tty" */
snprintf(sp->tty_str, sizeof(sp->tty_str), "%u,%u",
(tty >> 8) & 0xfff, /* major */
(tty & 0xff) | ((tty >> 12) & 0xfff00));
cp = skip_fields(cp, 6); /* tpgid, flags, min_flt, cmin_flt, maj_flt, cmaj_flt */
sp->utime = fast_strtoul_10(cp, &cp);
sp->stime = fast_strtoul_10(cp, &cp);
cp = skip_fields(cp, 3); /* cutime, cstime, priority */
tasknice = fast_strtoul_10(cp, &cp);
cp = skip_fields(cp, 3); /* timeout, it_real_value, start_time */
sp->vsz = fast_strtoul_10(cp, &cp) >> 10; /* vsize is in bytes and we want kb */
sp->rss = fast_strtoul_10(cp, &cp) >> 10;
#endif
if (sp->vsz == 0 && sp->state[0] != 'Z')
sp->state[1] = 'W';
else
@ -215,8 +268,6 @@ procps_status_t* procps_scan(procps_status_t* sp, int flags)
else
sp->state[2] = ' ';
sp->vsz = vsz >> 10; /* vsize is in bytes and we want kb */
sp->rss = rss >> 10;
}
if (flags & PSSCAN_CMD) {