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3afac4ce0

Denis Vlasenko

2007-06-19

FAILED Duration: 12s

Subject

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

Binary

No binary (build failed)

Architecture & Compiler Flags

Architecture: x86_64-linux-gnu Compiler: gcc (Ubuntu 11.4.0-1ubuntu1~22.04.3) 11.4.0

—

Build Log

(log yok)

Commit Diff GitHub →

libbb/Config.in +7 -0 libbb/procps.c +53 -2

libbb/Config.in+7 -0

@@ -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

libbb/procps.c+53 -2

@@ -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) {