Re: [PATCH 1/3] drm/xe/gt_stats: Detect and log overflow

[Matthew Auld <matthew.auld@intel.com>]

On 25/02/2025 13:17, Francois Dugast wrote:
> Check if the atomic counter limit has been reached and if that is the
> case, set the counter value to the new increment to prevent keeping
> a garbage value, and notify it in the kernel log as below:
> 
>      [drm:xe_gt_stats_incr [xe]] GT0: stats vma_pagefault_bytes overflow, resetting
> 
> Signed-off-by: Francois Dugast <francois.dugast@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>

> ---
>   drivers/gpu/drm/xe/xe_gt_stats.c | 18 ++++++++++++------
>   1 file changed, 12 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_gt_stats.c b/drivers/gpu/drm/xe/xe_gt_stats.c
> index 2e9879ea4674..753c081b68a6 100644
> --- a/drivers/gpu/drm/xe/xe_gt_stats.c
> +++ b/drivers/gpu/drm/xe/xe_gt_stats.c
> @@ -8,8 +8,15 @@
>   #include <drm/drm_print.h>
>   
>   #include "xe_gt.h"
> +#include "xe_gt_printk.h"
>   #include "xe_gt_stats.h"
>   
> +static const char *const stat_description[__XE_GT_STATS_NUM_IDS] = {
> +	"tlb_inval_count",
> +	"vma_pagefault_count",
> +	"vma_pagefault_bytes",
> +};
> +
>   /**
>    * xe_gt_stats_incr - Increments the specified stats counter
>    * @gt: GT structure
> @@ -24,13 +31,12 @@ void xe_gt_stats_incr(struct xe_gt *gt, const enum xe_gt_stats_id id, int incr)
>   		return;
>   
>   	atomic_add(incr, &gt->stats.counters[id]);
> -}
>   
> -static const char *const stat_description[__XE_GT_STATS_NUM_IDS] = {
> -	"tlb_inval_count",
> -	"vma_pagefault_count",
> -	"vma_pagefault_bytes",
> -};
> +	if (atomic_read(&gt->stats.counters[id]) < 0) {
> +		xe_gt_dbg(gt, "stats %s overflow, resetting\n", stat_description[id]);
> +		atomic_set(&gt->stats.counters[id], incr);
> +	}
> +}
>   
>   /**
>    * xe_gt_stats_print_info - Print the GT stats