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

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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
This commit is contained in:
Jim Warner 2012-02-03 00:00:00 -06:00 committed by Craig Small
parent f348575edc
commit a9041a5526
2 changed files with 7 additions and 1 deletions
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7
top/top.c
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@ -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

1
top/top.h
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@ -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 */