top: reduce % CPU distortions when a core was turned off

This patch provides for cpu cores which can be turned
off completely when idle (Nehalem, etc.) thus registering
very few or no tics since the last update cycle.

When CPU_ZEROTICS is not defined (the default), any
displayed cpu with less than a certain amount of total
tics will show as 100% idle.  That amount is tempered
by the delay interval and total number of cpus.

This commit also satisfies the Debian 'top_nohz' patch
(11/24/09) in a slightly more efficient manner.  That
patch concerned kernels built with CONFIG_NO_HZ.

Reference:
http://www.freelists.org/post/procps/CStates-handling-new-switch,4

diff --git a/top/top.c b/top/top.c
index 172507f8044362eff3862ae2b1f9593064ac5203..8d24962e4606f98e9452ca00d8e30c5726deb44b 100644 (file)
--- a/top/top.c
+++ b/top/top.c
@@ -3324,13 +3324,18 @@ static void summaryhlp (CPU_t *cpu, const char *pfx) {
    s_frme = TRIMz(cpu->cur.s - cpu->sav.s);
    n_frme = TRIMz(cpu->cur.n - cpu->sav.n);
    i_frme = TRIMz(cpu->cur.i - cpu->sav.i);
-   if ((u_frme == 0) && (i_frme == 0)) i_frme = 100;
    w_frme = TRIMz(cpu->cur.w - cpu->sav.w);
    x_frme = TRIMz(cpu->cur.x - cpu->sav.x);
    y_frme = TRIMz(cpu->cur.y - cpu->sav.y);
    z_frme = TRIMz(cpu->cur.z - cpu->sav.z);
    tot_frme = u_frme + s_frme + n_frme + i_frme + w_frme + x_frme + y_frme + z_frme;
+#ifdef CPU_ZEROTICS
    if (1 > tot_frme) tot_frme = 1;
+#else
+   if (tot_frme < ((smp_num_cpus * 10) * Rc.delay_time))
+      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
    scale = 100.0 / (float)tot_frme;
 
    /* display some kinda' cpu state percentages

diff --git a/top/top.h b/top/top.h
index 0abf9552fd23d8f9035dfac55914793ff186675c..c4daa1bb559387b07114b01b36f9d5595ae3c809 100644 (file)
--- a/top/top.h
+++ b/top/top.h
@@ -27,6 +27,7 @@
 //#define ATEOJ_RPTSTD            /* report on misc stuff, at end-of-job     */
 //#define CASEUP_HEXES            /* show any hex values in upper case       */
 //#define CASEUP_SUFIX            /* show time/mem/cnts suffix in upper case */
+//#define CPU_ZEROTICS            /* tolerate few tics when cpu off vs. idle */
 //#define EQUCOLHDRYES            /* yes, do equalize column header lengths  */
 //#define OFF_HST_HASH            /* use BOTH qsort+bsrch vs. hashing scheme */
 //#define OFF_STDIOLBF            /* disable our own stdout _IOFBF override  */