linux-kernel - [PATCH v2 3/4] soc: apple: rtkit: Use high prio work queue

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Message-Id: <20250226-apple-soc-misc-v2-3-c3ec37f9021b@svenpeter.dev>
Date: Wed, 26 Feb 2025 19:00:05 +0000
From: Sven Peter via B4 Relay <devnull+sven.svenpeter.dev@...nel.org>
To: Alyssa Rosenzweig <alyssa@...enzweig.io>, Janne Grunau <j@...nau.net>, 
 Sven Peter <sven@...npeter.dev>
Cc: asahi@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org, 
 linux-kernel@...r.kernel.org
Subject: [PATCH v2 3/4] soc: apple: rtkit: Use high prio work queue

From: Janne Grunau <j@...nau.net>

rtkit messages as communication with the DCP firmware for framebuffer
swaps or input events are time critical so use WQ_HIGHPRI to prevent
user space CPU load to increase latency.
With kwin_wayland 6's explicit sync mode user space load was able to
delay the IOMFB rtkit communication enough to miss vsync for surface
swaps. Minimal test scenario is constantly resizing a glxgears
Xwayland window.

Signed-off-by: Janne Grunau <j@...nau.net>
Reviewed-by: Alyssa Rosenzweig <alyssa@...enzweig.io>
Signed-off-by: Sven Peter <sven@...npeter.dev>
---
 drivers/soc/apple/rtkit.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/soc/apple/rtkit.c b/drivers/soc/apple/rtkit.c
index 7e7b4f64ab17..4b78463dd5a1 100644
--- a/drivers/soc/apple/rtkit.c
+++ b/drivers/soc/apple/rtkit.c
@@ -696,7 +696,7 @@ struct apple_rtkit *apple_rtkit_init(struct device *dev, void *cookie,
 	rtk->mbox->rx = apple_rtkit_rx;
 	rtk->mbox->cookie = rtk;
 
-	rtk->wq = alloc_ordered_workqueue("rtkit-%s", WQ_MEM_RECLAIM,
+	rtk->wq = alloc_ordered_workqueue("rtkit-%s", WQ_HIGHPRI | WQ_MEM_RECLAIM,
 					  dev_name(rtk->dev));
 	if (!rtk->wq) {
 		ret = -ENOMEM;

-- 
2.34.1