top: fixup logic for Nehalem cpu 'idle' threshold

Due to a poorly constructed temporary fprintf
used during development, an earlier commit went
a little too far in its computations.  The net
result was the code looked nice but actually
accomplished nothing.

It is the /proc/stat line 1 (summary line)
whose tics must be used in establishing the
threshold boundary.  And that calculation
need be performed just once per frame.

This commit ensures one threshold calculation
per delay interval no matter how many cpus
are ultimately displayed.

It also corrects scalability by factoring in
the total number of online processors.

Reference:
commit 9e7dd43ab7

top/top.c

@@ -1826,6 +1826,12 @@ static CPU_t *cpus_refresh (CPU_t *cpus) {
    cpus[Cpu_faux_tot].cur.tot = cpus[Cpu_faux_tot].cur.u + cpus[Cpu_faux_tot].cur.s
       + cpus[Cpu_faux_tot].cur.n + cpus[Cpu_faux_tot].cur.i + cpus[Cpu_faux_tot].cur.w
       + cpus[Cpu_faux_tot].cur.x + cpus[Cpu_faux_tot].cur.y + cpus[Cpu_faux_tot].cur.z;
+   /* if a Nehalem type cpu has been turned off completely, and thus registers
+      very few total tics, we'll force it to be treated as idle when that total
+      falls below a % of those expected -- other cpus will register their full
+      number of expected tics as 'idle' and thus won't be effected */
+   cpus[Cpu_faux_tot].edge =
+      ((cpus[Cpu_faux_tot].cur.tot - cpus[Cpu_faux_tot].sav.tot) / smp_num_cpus) / (100 / TICS_EDGE);
 
    // now value each separate cpu's tics, maybe
    for (i = 0; i < Cpu_faux_tot && i < Screen_rows; i++) {
@@ -1844,9 +1850,9 @@ static CPU_t *cpus_refresh (CPU_t *cpus) {
             memmove(&cpus[i], &cpus[Cpu_faux_tot], sizeof(CPU_t));
             break;        // tolerate cpus taken offline
       }
-      cpus[i].cur.tot = cpus[i].cur.u + cpus[i].cur.s
-         + cpus[i].cur.n + cpus[i].cur.i + cpus[i].cur.w
-         + cpus[i].cur.x + cpus[i].cur.y + cpus[i].cur.z;
+      cpus[i].edge = cpus[Cpu_faux_tot].edge;
+      // this is for symmetry only, it's not currently required
+      cpus[i].cur.tot = cpus[Cpu_faux_tot].cur.tot;
 #ifdef PRETEND4CPUS
       cpus[i].id = i;
 #endif
@@ -3338,7 +3344,7 @@ static void summaryhlp (CPU_t *cpu, const char *pfx) {
 #ifdef CPU_ZEROTICS
    if (1 > tot_frme) tot_frme = 1;
 #else
-   if (tot_frme < (cpu->cur.tot - cpu->sav.tot) / 10)
+   if (tot_frme < cpu->edge)
       tot_frme = u_frme = s_frme = n_frme = i_frme = w_frme = x_frme = y_frme = z_frme = 0;
    if (1 > tot_frme) i_frme = tot_frme = 1;
 #endif

top/top.h

@@ -129,6 +129,11 @@
            -- used at startup and for task/thread mode transitions */
 #define PROC_XTRA  -1
 
+        /* This is the % used in establishing the tics threshold below
+           which a cpu is treated as 'idle' rather than displaying
+           misleading state percentages */
+#define TICS_EDGE  20
+
 
 /* #####  Enum's and Typedef's  ############################################ */
 
@@ -214,12 +219,13 @@ typedef struct CT_t {
       2.6.0  kernel: x == hi (hardware irq time), y == si (software irq time)
       2.6.11 kernel: z == st (virtual steal time) */
    TIC_t u, n, s, i, w, x, y, z;  // as represented in /proc/stat
-   SIC_t tot;                     // total of above
+   SIC_t tot;                     // total from /proc/stat line 1
 } CT_t;
 
 typedef struct CPU_t {
    CT_t cur;                      // current frame's cpu tics
    CT_t sav;                      // prior frame's cpu tics
+   SIC_t edge;                    // tics adjustment threshold boundary
    int id;                        // the cpu id number (0 - nn)
 } CPU_t;