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

   text    data     bss     dec     hex filename
 734651    3040   14416  752107   b79eb busybox_old
 734751    3040   14416  752207   b7a4f busybox_unstripped

diff --git a/libbb/Config.in b/libbb/Config.in
index 5f4e416dd9dd1da5cde19a4131577e2b3a6331cd..f82a2b1cec71521f828540d5e4285501bcf69643 100644 (file)
--- a/libbb/Config.in
+++ b/libbb/Config.in
@@ -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

diff --git a/libbb/procps.c b/libbb/procps.c
index 1e2495a5ab8ad70903742904001a5f26572d5bc7..879cc105a00b53166cfe3529832b8920fc61ff94 100644 (file)
--- a/libbb/procps.c
+++ b/libbb/procps.c
@@ -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) {