From 435f523997caf85054192e4ff1bde9dcae4508a6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Henrik=20Rydg=C3=A5rd?= <hrydgard@gmail.com>
Date: Fri, 13 Jun 2025 23:31:02 +0200
Subject: [PATCH] Replacement textures: Don't spend frame time waiting for a
 texture to be finished

It's better to finish rendering the frame and have the texture ready for
the next one, without wasting CPU.

However, if the user set their texture load speed to "Instant", that
means they never want to see any original textures. So in that case, we
do still wait.

Fixes #20519
---
 Common/Thread/Waitable.h          |  4 ++--
 GPU/Common/ReplacedTexture.cpp    |  3 ++-
 GPU/Common/TextureCacheCommon.cpp | 11 +++++++++--
 3 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/Common/Thread/Waitable.h b/Common/Thread/Waitable.h
index de33ed2049..abda42fef9 100644
--- a/Common/Thread/Waitable.h
+++ b/Common/Thread/Waitable.h
@@ -25,11 +25,11 @@ public:
 		cond_.wait(lock, [&] { return triggered_.load(); });
 	}
 
-	bool WaitFor(double budget) {
+	bool WaitFor(double budget_s) {
 		if (triggered_)
 			return true;
 
-		uint32_t us = budget > 0 ? (uint32_t)(budget * 1000000.0) : 0;
+		uint32_t us = budget_s > 0 ? (uint32_t)(budget_s * 1000000.0) : 0;
 		if (us == 0)
 			return false;
 
diff --git a/GPU/Common/ReplacedTexture.cpp b/GPU/Common/ReplacedTexture.cpp
index ee1ef5e736..0950d00e54 100644
--- a/GPU/Common/ReplacedTexture.cpp
+++ b/GPU/Common/ReplacedTexture.cpp
@@ -176,7 +176,8 @@ bool ReplacedTexture::Poll(double budget) {
 	lastUsed_ = now;
 
 	// Let's not even start a new texture if we're already behind.
-	if (budget <= 0.0)
+	// Note that 0.0 is used as a signalling value that we don't want to wait (just handling already finished textures).
+	if (budget < 0.0)
 		return false;
 
 	_assert_(!threadWaitable_);
diff --git a/GPU/Common/TextureCacheCommon.cpp b/GPU/Common/TextureCacheCommon.cpp
index 80ab65b25e..259406e7ec 100644
--- a/GPU/Common/TextureCacheCommon.cpp
+++ b/GPU/Common/TextureCacheCommon.cpp
@@ -1594,12 +1594,19 @@ ReplacedTexture *TextureCacheCommon::FindReplacement(TexCacheEntry *entry, int *
 }
 
 void TextureCacheCommon::PollReplacement(TexCacheEntry *entry, int *w, int *h, int *d) {
-	double budget = replacementFrameBudgetSeconds_ - replacementTimeThisFrame_;
+	double waitBudget = replacementFrameBudgetSeconds_ - replacementTimeThisFrame_;
 	// Note: Don't avoid the Poll call if budget is 0, we do meaningful things there.
 	// Poll also handles negative budgets.
 
 	double replaceStart = time_now_d();
-	if (entry->replacedTexture->Poll(budget)) {
+
+	// Unless the mode is set to Instant (where the user explicitly wants to wait for each texture),
+	// it's just a waste of time to wait here really. OK, we might get a texture one frame early but
+	// we wasted a lot of time waiting, likely slowing down our framerate.
+	if (g_Config.iReplacementTextureLoadSpeed != ReplacementTextureLoadSpeed::INSTANT) {
+		waitBudget = 0.0;
+	}
+	if (entry->replacedTexture->Poll(waitBudget)) {
 		if (entry->replacedTexture->State() == ReplacementState::ACTIVE) {
 			entry->replacedTexture->GetSize(0, w, h);
 			// Consider it already "scaled.".