linux-kernel - Re: [PATCH v2] mm: kfence: print the elapsed time for allocated/freed track

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Message-ID: <CANpmjNMvdkn8Zw4SQy1n2e+HHvpg33fC9xmYkFD9fi6THNj_tQ@mail.gmail.com>
Date: Wed, 7 Aug 2024 12:39:50 +0200
From: Marco Elver <elver@...gle.com>
To: "qiwu.chen" <qiwuchen55@...il.com>, Alexander Potapenko <glider@...gle.com>
Cc: dvyukov@...gle.com, akpm@...ux-foundation.org, kasan-dev@...glegroups.com, 
	linux-mm@...ck.org, "qiwu.chen" <qiwu.chen@...nssion.com>, 
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] mm: kfence: print the elapsed time for allocated/freed track

On Wed, 7 Aug 2024 at 04:56, qiwu.chen <qiwuchen55@...il.com> wrote:
>
> Print the elapsed time for the allocated or freed track,
> which can be useful in some debugging scenarios.
>
> Signed-off-by: qiwu.chen <qiwu.chen@...nssion.com>

Reviewed-by: Marco Elver <elver@...gle.com>

Thanks for the changes! I think this is more generally useful and much
simpler than v1.

> ---
>  mm/kfence/report.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/mm/kfence/report.c b/mm/kfence/report.c
> index c509aed326ce..73a6fe42845a 100644
> --- a/mm/kfence/report.c
> +++ b/mm/kfence/report.c
> @@ -16,6 +16,7 @@
>  #include <linux/sprintf.h>
>  #include <linux/stacktrace.h>
>  #include <linux/string.h>
> +#include <linux/sched/clock.h>
>  #include <trace/events/error_report.h>
>
>  #include <asm/kfence.h>
> @@ -108,11 +109,14 @@ static void kfence_print_stack(struct seq_file *seq, const struct kfence_metadat
>         const struct kfence_track *track = show_alloc ? &meta->alloc_track : &meta->free_track;
>         u64 ts_sec = track->ts_nsec;
>         unsigned long rem_nsec = do_div(ts_sec, NSEC_PER_SEC);
> +       u64 interval_nsec = local_clock() - meta->alloc_track.ts_nsec;
> +       unsigned long rem_interval_nsec = do_div(interval_nsec, NSEC_PER_SEC);
>
>         /* Timestamp matches printk timestamp format. */
> -       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):\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);
>
>         if (track->num_stack_entries) {
>                 /* Skip allocation/free internals stack. */
> --
> 2.25.1
>
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