From 1e3218bc5ba2b739261f0c0bacf4eb662d377236 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Michel=20D=C3=A4nzer?= Date: Wed, 17 Aug 2016 17:02:04 +0900 Subject: [PATCH] loader/dri3: Overhaul dri3_update_num_back Always use 3 buffers when flipping. With only 2 buffers, we have to wait for a flip to complete (which takes non-0 time even with asynchronous flips) before we can start working on the next frame. We were previously only using 2 buffers for flipping if the X server supports asynchronous flips, even when we're not using asynchronous flips. This could result in bad performance (the referenced bug report is an extreme case, where the inter-frame stalls were preventing the GPU from reaching its maximum clocks). I couldn't measure any performance boost using 4 buffers with flipping. Performance actually seemed to go down slightly, but that might have been just noise. Without flipping, a single back buffer is enough for swap interval 0, but we need to use 2 back buffers when the swap interval is non-0, otherwise we have to wait for the swap interval to pass before we can start working on the next frame. This condition was previously reversed. Cc: "12.0 11.2" Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=97260 Reviewed-by: Frank Binns Reviewed-by: Eric Anholt --- src/loader/loader_dri3_helper.c | 15 ++++++--------- 1 file changed, 6 insertions(+), 9 deletions(-) diff --git a/src/loader/loader_dri3_helper.c b/src/loader/loader_dri3_helper.c index e9fb97bfaf7..86ae5aecd5f 100644 --- a/src/loader/loader_dri3_helper.c +++ b/src/loader/loader_dri3_helper.c @@ -68,15 +68,12 @@ dri3_fence_await(xcb_connection_t *c, struct loader_dri3_buffer *buffer) static void dri3_update_num_back(struct loader_dri3_drawable *draw) { - draw->num_back = 1; - if (draw->flipping) { - if (!draw->is_pixmap && - !(draw->present_capabilities & XCB_PRESENT_CAPABILITY_ASYNC)) - draw->num_back++; - draw->num_back++; - } - if (draw->vtable->get_swap_interval(draw) == 0) - draw->num_back++; + if (draw->flipping) + draw->num_back = 3; + else if (draw->vtable->get_swap_interval(draw) != 0) + draw->num_back = 2; + else + draw->num_back = 1; } void -- 2.30.2