Re: [PATCH v8 06/11] fs: add percpu counters for significant multigrain timestamp events
From: Thomas Gleixner
Date: Mon Sep 16 2024 - 06:21:00 EST
On Sat, Sep 14 2024 at 13:07, Jeff Layton wrote:
> fs/inode.c | 76 ++++++++++++++++++++++++++++++++++++--
> include/linux/timekeeping.h | 1 +
> kernel/time/timekeeping.c | 3 +-
> kernel/time/timekeeping_debug.c | 12 ++++++
> kernel/time/timekeeping_internal.h | 3 ++
So the subject says 'fs:'. This is not how it works.
Provide the timekeeping changes in a separate patch and then add the fs
voodoo. Documentation is pretty clear about this, no?
> diff --git a/kernel/time/timekeeping_debug.c b/kernel/time/timekeeping_debug.c
> index b73e8850e58d..9a3792072762 100644
> --- a/kernel/time/timekeeping_debug.c
> +++ b/kernel/time/timekeeping_debug.c
> @@ -17,6 +17,9 @@
>
> #define NUM_BINS 32
>
> +/* incremented every time mg_floor is updated */
Sentences start with a uppercase letter.
> +DEFINE_PER_CPU(long, mg_floor_swaps);
Why is this long? This is a counter which always counts up..
> static unsigned int sleep_time_bin[NUM_BINS] = {0};
>
> static int tk_debug_sleep_time_show(struct seq_file *s, void *data)
> @@ -53,3 +56,12 @@ void tk_debug_account_sleep_time(const struct timespec64 *t)
> (s64)t->tv_sec, t->tv_nsec / NSEC_PER_MSEC);
> }
>
> +long get_mg_floor_swaps(void)
Can we please have a proper subsystem prefix and not this get_*()
notation. It's horrible to grep for. timekeeping_mg_get_...() makes it
clear where this function belongs to, no?
> +{
> + int i;
> + long sum = 0;
https://www.kernel.org/doc/html/latest/process/maintainer-tip.html#variable-declarations
Also please use 'cpu' instead of 'i'. Self explanatory variable names
have a value.
> + for_each_possible_cpu(i)
> + sum += per_cpu(mg_floor_swaps, i);
This needs annotation for kcsan as this is a racy access.
> + return sum < 0 ? 0 : sum;
> +}
> diff --git a/kernel/time/timekeeping_internal.h b/kernel/time/timekeeping_internal.h
> index 4ca2787d1642..2b49332b45a5 100644
> --- a/kernel/time/timekeeping_internal.h
> +++ b/kernel/time/timekeeping_internal.h
> @@ -11,8 +11,11 @@
> */
> #ifdef CONFIG_DEBUG_FS
> extern void tk_debug_account_sleep_time(const struct timespec64 *t);
> +DECLARE_PER_CPU(long, mg_floor_swaps);
> +#define mgtime_counter_inc(__var) this_cpu_inc(__var)
Please use static inlines for this.
Thanks,
tglx