GPU: Adjust memory and use the soft-limit.

ui/gl/gl_context_android.cc

Index: ui/gl/gl_context_android.cc
diff --git a/ui/gl/gl_context_android.cc b/ui/gl/gl_context_android.cc
index a9e888b203d41a2912d0e87217ae1a415660013a..1ba8939e6007074f7de83cfc04ca25ea19d00be6 100644
--- a/ui/gl/gl_context_android.cc
+++ b/ui/gl/gl_context_android.cc
@@ -108,27 +108,33 @@ bool GLContextEGL::GetTotalGpuMemory(size_t* bytes) {
   // Now we take a default of 1/8th of memory on high-memory devices,

[aelias_OOO_until_Jul13, 2014/02/15 00:55:17]

I think we should include screen resolution as part of this calculation as well
as device memory.  On the Nexus 4, 128MB is 32 viewports of prepaint, still
overkill.  Probably we should never go over 10 viewports of prepaint.

[epenner, 2014/02/15 01:02:27]

If you look at the history of this code, we have gone back and forth between
resolution and memory quite a bit. Memory was used in the end since this is a
hard limit spread across all GPU clients (in theory), and screen resolution was
hampering high-end devices.

I think the planned 'implicit' limit will solve this without needing to use
screen resolution here. The implicit limit will only use as much as the content
requires. With enough content it will scale up nicely all the way to the soft
limit, and then it has the hard-limit for extremes.

   // and gradually scale that back for low-memory devices (to be nicer
   // to other apps so they don't get killed). Examples:
-  // Nexus 4/10(2GB)    256MB
-  // Droid Razr M(1GB)  91MB
-  // Galaxy Nexus(1GB)  85MB
-  // Xoom(1GB)          85MB
-  // Nexus S(low-end)   8MB
+  // Nexus 4/10(2GB)    256MB (normally 128MB)
+  // Droid Razr M(1GB)  114MB (normally 57MB)
+  // Galaxy Nexus(1GB)  100MB (normally 50MB)
+  // Xoom(1GB)          100MB (normally 50MB)
+  // Nexus S(low-end)   12MB (normally 8MB)
+  // Note that the compositor now uses only some of this memory for
+  // pre-painting and uses the rest only for 'emergencies'.
   static size_t limit_bytes = 0;
   if (limit_bytes == 0) {
+    // NOTE: Non-low-end devices use only 50% of these limites,

[aelias_OOO_until_Jul13, 2014/02/15 00:55:17]

typo: should be "limits"

[epenner, 2014/02/15 01:02:27]

Done.

+    // except during 'emergencies' where 100% can be used.
     if (!base::android::SysUtils::IsLowEndDevice()) {
       if (physical_memory_mb >= 1536)
-        limit_bytes = physical_memory_mb / 8;
+        limit_bytes = physical_memory_mb / 8; // >192MB
       else if (physical_memory_mb >= 1152)
-        limit_bytes = physical_memory_mb / 10;
+        limit_bytes = physical_memory_mb / 8; // >144MB
       else if (physical_memory_mb >= 768)
-        limit_bytes = physical_memory_mb / 12;
+        limit_bytes = physical_memory_mb / 10; // >76MB
       else
-        limit_bytes = physical_memory_mb / 16;
+        limit_bytes = physical_memory_mb / 12; // <64MB
     } else {
       // Low-end devices have 512MB or less memory by definition
       // so we hard code the limit rather than relying on the heuristics
       // above. Low-end devices use 4444 textures so we can use a lower limit.
-      limit_bytes = 8;
+      // NOTE: Low-end uses 2/3 (67%) of this memory in practice, so we have
+      // increased the limit to 12 (8MB, or 12MB in emergencies).
+      limit_bytes = 12;
     }
     limit_bytes = limit_bytes * 1024 * 1024;
   }