egl image creation in case of atomic

Hosokawa, Kenji (ADITG/ESB) khosokawa at
Tue Aug 28 12:10:06 UTC 2018


When eglSwapInterval is 0, clients may send buffers without waiting frame callbacks. Currently, egl image is created when a buffer is committed from client. But egl image is only needed, when gl-renderer is used to render the framebuffer. Creating an egl image in every commit causes additional CPU load in weston when clients are sending more buffers than display refresh rate. Furthermore, creating egl images are not needed at all, when the client buffer can be imported to a DRM plane. We would like to reduce CPU usage of weston in that case.
In my investigation, egl image creation can produce higher CPU load in Weston. I tried to remove egl image creation with this simple ugly patch for weston.

diff --git a/libweston/gl-renderer.c b/libweston/gl-renderer.c
index 2c50d2d..bbb5846 100644
--- a/libweston/gl-renderer.c
+++ b/libweston/gl-renderer.c
@@ -2260,6 +2260,8 @@ gl_renderer_attach_dmabuf(struct weston_surface *surface,
        buffer->y_inverted =
                !(dmabuf->attributes.flags & ZWP_LINUX_BUFFER_PARAMS_V1_FLAGS_Y_INVERT);

+       return;
        for (i = 0; i < gs->num_images; i++)
        gs->num_images = 0;

Without the patch (original), total CPU usage of weston was 25%. With the patch, it was decreased to 10%.
I used weston v4.0.92, weston-simple-egl with -o and -b options, rcar h3 target. It was measured with top command simply.

My question is that can egl image creation be postponed until repaint output (gl_renderer_repaint_output)?

Best regards

Kenji Hosokawa
Engineering Software Base (ADITG/ESB)
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