top's CPUn vs C column

[John Baldwin]

On Friday, March 01, 2013 1:17:41 pm Chris Ross wrote:
> 
>   So, I was looking at a v240 I have running stable/9 (9.1-STABLE), and 
noticed something odd.  The per-CPU information displayed by top seems 
inconsistent.  To simplify things, while I'm running a "make release" in 
/usr/src/release, I just started running the following command over and over 
(by hand):
> 
> cross: top | grep " CPU"
> cross: top | grep " CPU"
>  1044 cross         1  72    0 17128K  4464K CPU1    0   0:01  1.27% zsh
> 22528 root          1  77    5 11672K  2592K CPU1    1   0:00  0.00% sh
> cross: top | grep " CPU"
> cross: top | grep " CPU"
> 22634 cross         1  72    0 12808K  2872K CPU1    1   0:00  0.00% top
> 22633 root          1  77    5  6272K   880K CPU0    1   0:00  0.00% make
> cross: top | grep " CPU"
> 22637 root          1  77    5  6272K  1656K CPU0    0   0:00  0.00% make
> cross: top | grep " CPU"
> cross: top | grep " CPU"
> 22684 root          1  77    5 11672K  2592K CPU0    0   0:00  0.00% sh
> cross:
> 
>   This displayed what I had earlier seen in the full-screen top.  There 
doesn't appear to be any specific binding between the "n" in the "CPUn" state 
value, and the number in the "C" column, which is according to the man page, 
should mean the same thing.

No, they are different things.  The man page is a bit stale.  The 'C' column 
is the CPU that the process last ran on.  Hmm, it's actually easiest to fix 
the code I think.  Try this (untested) change:

Index: usr.bin/top/machine.c
===================================================================
--- machine.c	(revision 247792)
+++ machine.c	(working copy)
@@ -797,7 +797,7 @@ format_next_process(caddr_t handle, char *(*get_us
 	double pct;
 	struct handle *hp;
 	char status[16];
-	int state;
+	int cpu, state;
 	struct rusage ru, *rup;
 	long p_tot, s_tot;
 	char *proc_fmt, thr_buf[6], jid_buf[6];
@@ -997,6 +997,13 @@ format_next_process(caddr_t handle, char *(*get_us
 	}
 
 	/* format this entry */
+	if (smpmode) {
+		if (state == SRUN && pp->ki_oncpu != 0xff)
+			cpu = pp->ki_oncpu;
+		else
+			cpu = pp->ki_lastcpu;
+	} else
+		cpu = 0;
 	proc_fmt = smpmode ? smp_Proc_format : up_Proc_format;
 	if (ps.thread != 0)
 		thr_buf[0] = '\0';
@@ -1014,7 +1021,7 @@ format_next_process(caddr_t handle, char *(*get_us
 	    format_k2(PROCSIZE(pp)),
 	    format_k2(pagetok(pp->ki_rssize)),
 	    status,
-	    smpmode ? pp->ki_lastcpu : 0,
+	    cpu,
 	    format_time(cputime),
 	    ps.wcpu ? 100.0 * weighted_cpu(pct, pp) : 100.0 * pct,
 	    screen_width > cmdlengthdelta ? screen_width - cmdlengthdelta : 0,

-- 
John Baldwin