linux-kernel - [PATCH v6 6/6] drm/drm-file: Show finer-grained BO sizes in drm_show_memory

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Date:   Wed, 20 Sep 2023 00:34:54 +0100
From:   Adrián Larumbe <adrian.larumbe@...labora.com>
To:     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
Cc:     adrian.larumbe@...labora.com, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        freedreno@...ts.freedesktop.org, healych@...zon.com,
        kernel@...labora.com,
        Boris Brezillon <boris.brezillon@...labora.com>
Subject: [PATCH v6 6/6] drm/drm-file: Show finer-grained BO sizes in drm_show_memory_stats

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 contexts of low memory
usage.

The new selection criteria try to preserve precision, whilst also
increasing the display unit selection threshold to render more accurate
values.

Signed-off-by: Adrián Larumbe <adrian.larumbe@...labora.com>
Reviewed-by: Boris Brezillon <boris.brezillon@...labora.com>
Reviewed-by: Steven Price <steven.price@....com>
---
 drivers/gpu/drm/drm_file.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
index 762965e3d503..34cfa128ffe5 100644
--- a/drivers/gpu/drm/drm_file.c
+++ b/drivers/gpu/drm/drm_file.c
@@ -872,6 +872,8 @@ void drm_send_event(struct drm_device *dev, struct drm_pending_event *e)
 }
 EXPORT_SYMBOL(drm_send_event);
 
+#define UPPER_UNIT_THRESHOLD 100
+
 static void print_size(struct drm_printer *p, const char *stat,
 		       const char *region, u64 sz)
 {
@@ -879,7 +881,8 @@ 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)) &&
+		    sz < UPPER_UNIT_THRESHOLD * SZ_1K)
 			break;
 		sz = div_u64(sz, SZ_1K);
 	}
-- 
2.42.0