From c62b33d8c1f94d08cf1843701232f70d62425f2a Mon Sep 17 00:00:00 2001
From: Alex Deucher <alexander.deucher@amd.com>
Date: Thu, 19 May 2022 10:21:08 -0400
Subject: drm/amdgpu: Adjust logic around GTT size (v3)
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Git-commit: f15345a377c6ea9c7cc74f079616af8856aff37f
Patch-mainline: v5.19-rc4
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225

Certain GL unit tests for large textures can cause problems
with the OOM killer since there is no way to link this memory
to a process.  This was originally mitigated (but not necessarily
eliminated) by limiting the GTT size.  The problem is this limit
is often too low for many modern games so just make the limit 1/2
of system memory. The OOM accounting needs to be addressed, but
we shouldn't prevent common 3D applications from being usable
just to potentially mitigate that corner case.

Set default GTT size to max(3G, 1/2 of system ram) by default.

v2: drop previous logic and default to 3/4 of ram
v3: default to half of ram to align with ttm
v4: fix spelling in comment (Kent)

Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/1942
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index be6f76a30ac6..3b4c19412625 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -1798,18 +1798,26 @@ int amdgpu_ttm_init(struct amdgpu_device *adev)
 	DRM_INFO("amdgpu: %uM of VRAM memory ready\n",
 		 (unsigned) (adev->gmc.real_vram_size / (1024 * 1024)));
 
-	/* Compute GTT size, either bsaed on 3/4th the size of RAM size
+	/* Compute GTT size, either based on 1/2 the size of RAM size
 	 * or whatever the user passed on module init */
 	if (amdgpu_gtt_size == -1) {
 		struct sysinfo si;
 
 		si_meminfo(&si);
-		gtt_size = min(max((AMDGPU_DEFAULT_GTT_SIZE_MB << 20),
-			       adev->gmc.mc_vram_size),
-			       ((uint64_t)si.totalram * si.mem_unit * 3/4));
-	}
-	else
+		/* Certain GL unit tests for large textures can cause problems
+		 * with the OOM killer since there is no way to link this memory
+		 * to a process.  This was originally mitigated (but not necessarily
+		 * eliminated) by limiting the GTT size.  The problem is this limit
+		 * is often too low for many modern games so just make the limit 1/2
+		 * of system memory which aligns with TTM. The OOM accounting needs
+		 * to be addressed, but we shouldn't prevent common 3D applications
+		 * from being usable just to potentially mitigate that corner case.
+		 */
+		gtt_size = max((AMDGPU_DEFAULT_GTT_SIZE_MB << 20),
+			       (u64)si.totalram * si.mem_unit / 2);
+	} else {
 		gtt_size = (uint64_t)amdgpu_gtt_size << 20;
+	}
 
 	/* Initialize GTT memory pool */
 	r = amdgpu_gtt_mgr_init(adev, gtt_size);
-- 
2.38.1