[Crash-utility] [PATCH v2] kmem: Add support to -S option to specify a range of CPU-specific slab data

[HAGIO KAZUHITO(萩尾 一仁)]

-----Original Message-----
> 
> On Fri 2021-07-16 07:32 +0000, HAGIO KAZUHITO(萩尾 一仁) wrote:
> 
> Kazu,
> 
> > Thanks for the update.
> 
> No problem.
> 
> > > +				for (i = 0; i < kt->cpus; i++)
> > > +					if (NUM_IN_BITMAP(cpus, i) && check_offline_cpu(i))
> > > +						error(INFO, "CPU %d is OFFLINE.\n", i);
> >
> > With the offline hide option, "CPU xx [OFFLINE]" is shown as follows and
> > this error message is not needed.
> >
> > crash> set offline hide
> >       offline: hide
> > crash> kmem -S=15 TCP
> > kmem: CPU 15 is OFFLINE.
> > CACHE             OBJSIZE  ALLOCATED     TOTAL  SLABS  SSIZE  NAME
> > ffff916f6798b2c0     2440         17       208     16    32k  TCP
> > CPU 15 [OFFLINE]
> > ...
> 
> The above was indeed intentional (to be more verbose) since the CPU(s)
> is/are explicitly specified by the user.

I see.  I think that it's good to have a way to know which CPUs are
offline without the offline hide option by another patch, as crash
shows only the number of offline CPUs when startup.

display_sys_stats() might be a good place to do something about it,
a simple example:

# crash
...
    DUMPFILE: /proc/kcore
        CPUS: 16 [OFFLINE: 2 (CPU: 14,15)]

--- a/kernel.c
+++ b/kernel.c
@@ -5627,9 +5627,22 @@ display_sys_stats(void)
                fprintf(fp, "        CPUS: %d\n", get_cpus_to_display());
        else {
                fprintf(fp, "        CPUS: %d", kt->cpus);
-               if (kt->cpus - get_cpus_to_display())
-                       fprintf(fp, " [OFFLINE: %d]", 
-                               kt->cpus - get_cpus_to_display());
+               if (kt->cpus - get_cpus_to_display()) {
+                       int i;
+                       char *p = buf;
+                       BZERO(buf, BUFSIZE);
+                       for (i = 0; i < kt->cpus; i++) {
+                               if (check_offline_cpu(i)) {
+                                       if (p == buf)
+                                               sprintf(p, "%d", i);
+                                       else
+                                               sprintf(p, ",%d", i);
+                                       p += strlen(p);
+                               }
+                       }
+                       fprintf(fp, " [OFFLINE: %d (CPU: %s)]", 
+                               kt->cpus - get_cpus_to_display(), buf);
+               }
                fprintf(fp, "\n");
        }

Thanks,
Kazu

> 
> > And the other commands do not say anything by default (offline show),
> > it should be the same behavior with them.
> 
> Fair enough. Better to remain consistent.
> 
> > So with removing the for block above, (but you don't need to repost)
> > Acked-by: Kazuhito Hagio <k-hagio-ab at nec.com>
> 
> Understood and thank you.
> 
> 
> 
> 
> 
> Kind regards,
> 
> --
> Aaron Tomlin