From bbca7c48111e4cac172ba1edd11cd2adc36a74fd Mon Sep 17 00:00:00 2001
From: Chris Jones <jones.chris.g@gmail.com>
Date: Mon, 27 Sep 2010 19:59:43 -0500
Subject: [PATCH] Bug 599562: Allocate cross-process layers surfaces from SyS V
 shm instead of /dev/shm to avoid being arbitrarily capped on maemo5/N900.
 r=stuart a=blocking-fennec

---
 gfx/layers/ipc/ShadowLayers.cpp | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/gfx/layers/ipc/ShadowLayers.cpp b/gfx/layers/ipc/ShadowLayers.cpp
index fcd7138a053..e1c324f0695 100644
--- a/gfx/layers/ipc/ShadowLayers.cpp
+++ b/gfx/layers/ipc/ShadowLayers.cpp
@@ -43,12 +43,15 @@
 
 #include "gfxSharedImageSurface.h"
 
+#include "mozilla/ipc/SharedMemorySysV.h"
 #include "mozilla/layers/PLayerChild.h"
 #include "mozilla/layers/PLayersChild.h"
 #include "mozilla/layers/PLayersParent.h"
 #include "ShadowLayers.h"
 #include "ShadowLayerChild.h"
 
+using namespace mozilla::ipc;
+
 namespace mozilla {
 namespace layers {
 
@@ -382,6 +385,21 @@ OptimalFormatFor(gfxASurface::gfxContentType aContent)
   }
 }
 
+static SharedMemory::SharedMemoryType
+OptimalShmemType()
+{
+#if defined(MOZ_PLATFORM_MAEMO) && defined(MOZ_HAVE_SHAREDMEMORYSYSV)
+  // Use SysV memory because maemo5 on the N900 only allots 64MB to
+  // /dev/shm, even though it has 1GB(!!) of system memory.  Sys V shm
+  // is allocated from a different pool.  We don't want an arbitrary
+  // cap that's much much lower than available memory on the memory we
+  // use for layers.
+  return SharedMemory::TYPE_SYSV;
+#else
+  return SharedMemory::TYPE_BASIC;
+#endif
+}
+
 PRBool
 ShadowLayerForwarder::AllocDoubleBuffer(const gfxIntSize& aSize,
                                         gfxASurface::gfxContentType aContent,
@@ -391,10 +409,12 @@ ShadowLayerForwarder::AllocDoubleBuffer(const gfxIntSize& aSize,
   NS_ABORT_IF_FALSE(HasShadowManager(), "no manager to forward to");
 
   gfxASurface::gfxImageFormat format = OptimalFormatFor(aContent);
+  SharedMemory::SharedMemoryType shmemType = OptimalShmemType();
+
   nsRefPtr<gfxSharedImageSurface> front = new gfxSharedImageSurface();
   nsRefPtr<gfxSharedImageSurface> back = new gfxSharedImageSurface();
-  if (!front->Init(mShadowManager, aSize, format) ||
-      !back->Init(mShadowManager, aSize, format))
+  if (!front->Init(mShadowManager, aSize, format, shmemType) ||
+      !back->Init(mShadowManager, aSize, format, shmemType))
     return PR_FALSE;
 
   *aFrontBuffer = NULL;       *aBackBuffer = NULL;