Re: [PATCH] mm: kfence: print the age time for alloacted objectes to trace memleak

[chenqiwu <qiwuchen55@gmail.com>]

On Mon, Aug 05, 2024 at 08:50:57AM +0200, Marco Elver wrote:
> 
> The "allocated/freed" info is superfluous, as freed objects will have
> a free stack.
> 
> Consider a slightly better script vs. just using grep.
Well, I think using grep is eaiser than a script to find leaks by a
large number of alloc tracks.

> /sys/kernel/debug/kfence/objects is of secondary concern and was added
> primarily as a debugging aid for KFENCE developers. We never thought
> it could be used to look for leaks, but good you found another use for
> it. ;-)
> The priority is to keep regular error reports generated by KFENCE
> readable. Adding this "allocated/freed" info just makes the line
> longer and is not useful.
>
How about print meta->state directly to get the object state for its
alloc/free track?
-       seq_con_printf(seq, "%s by task %d on cpu %d at %lu.%06lus:\n",
+       seq_con_printf(seq, "%s by task %d on cpu %d at %lu.%06lus (%lu.%06lus ago) state %d:\n",
                       show_alloc ? "allocated" : "freed", track->pid,
-                      track->cpu, (unsigned long)ts_sec, rem_nsec / 1000);
+                      track->cpu, (unsigned long)ts_sec, rem_nsec / 1000,
+                      (unsigned long)interval_nsec, rem_interval_nsec / 1000,
+                      meta->state);
> I'm happy with the "(%lu.%06lus ago)" part alone.
If it's still a not good idea, I will follow your suggestion and resend
it as v2.

Thanks
Qiwu