Commit 19b99719 authored by Mikulas Patocka's avatar Mikulas Patocka Committed by Greg Kroah-Hartman

udlfb: set optimal write delay

commit bb24153a upstream.

The default delay 5 jiffies is too much when the kernel is compiled with
HZ=100 - it results in jumpy cursor in Xwindow.

In order to find out the optimal delay, I benchmarked the driver on
1280x720x30fps video. I found out that with HZ=1000, 10ms is acceptable,
but with HZ=250 or HZ=300, we need 4ms, so that the video is played
without any frame skips.

This patch changes the delay to this value.
Signed-off-by: default avatarMikulas Patocka <>
Signed-off-by: default avatarBartlomiej Zolnierkiewicz <>
Signed-off-by: default avatarGreg Kroah-Hartman <>
parent d0f2eb3a
......@@ -88,7 +88,7 @@ struct dlfb_data {
#define DL_DEFIO_WRITE_DELAY 5 /* fb_deferred_io.delay in jiffies */
#define DL_DEFIO_WRITE_DELAY msecs_to_jiffies(HZ <= 300 ? 4 : 10) /* optimal value for 720p video */
#define DL_DEFIO_WRITE_DISABLE (HZ*60) /* "disable" with long delay */
/* remove these once align.h patch is taken into kernel */
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