linux-kernel - Re: [PATCH v4 6/6] drm/drm-file: Show finer-grained BO sizes in drm_show_memory

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Message-ID: <20230912113210.65897aab@collabora.com>
Date:   Tue, 12 Sep 2023 11:32:10 +0200
From:   Boris Brezillon <boris.brezillon@...labora.com>
To:     Adrián Larumbe <adrian.larumbe@...labora.com>
Cc:     maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
        tzimmermann@...e.de, airlied@...il.com, daniel@...ll.ch,
        robdclark@...il.com, quic_abhinavk@...cinc.com,
        dmitry.baryshkov@...aro.org, sean@...rly.run,
        marijn.suijten@...ainline.org, robh@...nel.org,
        steven.price@....com, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        healych@...zon.com, kernel@...labora.com,
        freedreno@...ts.freedesktop.org
Subject: Re: [PATCH v4 6/6] drm/drm-file: Show finer-grained BO sizes in
 drm_show_memory_stats

On Tue, 12 Sep 2023 09:37:00 +0100
Adrián Larumbe <adrian.larumbe@...labora.com> wrote:

> The current implementation will try to pick the highest available size
> display unit as soon as the BO size exceeds that of the previous
> multiplier. That can lead to loss of precision in BO's whose size is
> not a multiple of a MiB.
> 
> Fix it by changing the unit selection criteria.
> 
> For much bigger BO's, their size will naturally be aligned on something
> bigger than a 4 KiB page, so in practice it is very unlikely their display
> unit would default to KiB.

Let's wait for Rob's opinion on this.

> 
> Signed-off-by: Adrián Larumbe <adrian.larumbe@...labora.com>
> ---
>  drivers/gpu/drm/drm_file.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
> index 762965e3d503..bf7d2fe46bfa 100644
> --- a/drivers/gpu/drm/drm_file.c
> +++ b/drivers/gpu/drm/drm_file.c
> @@ -879,7 +879,7 @@ static void print_size(struct drm_printer *p, const char *stat,
>  	unsigned u;
>  
>  	for (u = 0; u < ARRAY_SIZE(units) - 1; u++) {
> -		if (sz < SZ_1K)
> +		if (sz & (SZ_1K - 1))
>  			break;
>  		sz = div_u64(sz, SZ_1K);
>  	}