ANDROID: x86_64: Set default max-page-size to 16kB #87413
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Android now supports both 4kB and 16kB page sizes. The vast majority of android apps developed on x86_64 machines. In order to provide emulators that support larger page sizes, Android emulates the page-size in x86_64 to support testing apps for large page size support. For this reason, update Android x86_64 ELFs default max-page-size to 16384 to support both 4kB and 16kB page-size devices. It raises the concern of increased disk space and extra VMA slab memory. In Android, RO partitions use sparse images, so that the holes on ELFs don't allocate blocks on disk; and PackageManger ensures to punch holes in ELF-paddings on the /data partition when an app is installed. Extra VMA slab memory is addressed by the bionic loader, which extends segment VMAs to cover the gaps between consecutive segment mappings, to avoid the extra VMAs needed for the gap PROT_NONE mappings (---p). This optimization is done in the crt_pad_segment note [1] is present in the ELF. [1] https://cs.android.com/android/platform/superproject/main/+/189e480390ef13199d59e1fb54078e8b78ea6f79:bionic/libc/arch-common/bionic/crt_pad_segment.S Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
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Can you add a test similar to #70251? |
llvmbot
added
clang
|
@llvm/pr-subscribers-clang @llvm/pr-subscribers-clang-driver Author: Kalesh Singh (Kalesh-Singh) ChangesAndroid now supports both 4kB and 16kB page sizes. The vast majority of android apps are developed on x86_64 machines. In order to provide emulators that support larger page sizes, Android emulates the page-size in x86_64 to support testing apps for large page size support. For this reason, update Android x86_64 ELFs default max-page-size to 16384 to support both 4kB and 16kB page-size devices. Increase max-page-size raises concerns of increased disk space and extra VMA slab memory. In Android, RO partitions use sparse images, so that the holes on ELFs don't allocate blocks on disk; and PackageManager ensures to punch holes in ELF-paddings on the /data partition when apps are installed. Extra VMA slab memory is addressed by the bionic loader, which extends segment VMAs to cover the gaps between consecutive segment mappings, to avoid the extra VMAs needed for the gap PROT_NONE mappings (---p). This optimization is done in the crt_pad_segment note [1] is present in the ELF. Full diff: https://github.com/llvm/llvm-project/pull/87413.diff 1 Files Affected:
diff --git a/clang/lib/Driver/ToolChains/Linux.cpp b/clang/lib/Driver/ToolChains/Linux.cpp
index 6c2f23e57bce05..fb65881061effc 100644
--- a/clang/lib/Driver/ToolChains/Linux.cpp
+++ b/clang/lib/Driver/ToolChains/Linux.cpp
@@ -244,8 +244,9 @@ Linux::Linux(const Driver &D, const llvm::Triple &Triple, const ArgList &Args)
// Android ARM uses max-page-size=4096 to reduce VMA usage.
ExtraOpts.push_back("-z");
ExtraOpts.push_back("max-page-size=4096");
- } else if (Triple.isAArch64()) {
+ } else if (Triple.isAArch64() || Triple.getArch() == llvm::Triple::x86_64) {
// Android AArch64 uses max-page-size=16384 to support 4k/16k page sizes.
+ // Android emulates a 16k page size for app testing on x86_64 machines.
ExtraOpts.push_back("-z");
ExtraOpts.push_back("max-page-size=16384");
}
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Added tests for x86[_64], thanks |
pirama-arumuga-nainar
approved these changes
Apr 11, 2024
MaskRay
reviewed
Apr 11, 2024
MaskRay
reviewed
Apr 11, 2024
Remove ^//$ lines and use --target= instead of -target which has been deprecated. Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
MaskRay
approved these changes
Apr 12, 2024
bazuzi
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Apr 15, 2024
Android now supports both 4kB and 16kB page sizes. The vast majority of android apps are developed on x86_64 machines. In order to provide emulators that support larger page sizes, Android emulates the page-size in x86_64 to support testing apps for large page size support. For this reason, update Android x86_64 ELFs default max-page-size to 16384 to support both 4kB and 16kB page-size devices. Increase max-page-size raises concerns of increased disk space and extra VMA slab memory. In Android, RO partitions use sparse images, so that the holes on ELFs don't allocate blocks on disk; and PackageManager ensures to punch holes in ELF-paddings on the /data partition when apps are installed. Extra VMA slab memory is addressed by the bionic loader, which extends segment VMAs to cover the gaps between consecutive segment mappings, to avoid the extra VMAs needed for the gap PROT_NONE mappings (---p). This optimization is done in the crt_pad_segment note [1] is present in the ELF. [1] https://cs.android.com/android/platform/superproject/main/+/189e480390ef13199d59e1fb54078e8b78ea6f79:bionic/libc/arch-common/bionic/crt_pad_segment.S --------- Signed-off-by: Kalesh Singh <kaleshsingh@google.com> Co-authored-by: Kalesh Singh <kaleshsingh@google.com>
Kalesh-Singh
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Apr 30, 2024
Starting from V, android introduces support for 16kB page sizes. The NDK [1] and toolchain [2][3] have been updated to support the larger page size. Update GDX build rules for android to use a 16kB max page size. [1] https://github.com/android/ndk/wiki/Changelog-r27#announcements [2] llvm/llvm-project#70251 [3] llvm/llvm-project#87413 Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
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Android now supports both 4kB and 16kB page sizes. The vast majority of android apps are developed on x86_64 machines. In order to provide emulators that support larger page sizes, Android emulates the page-size in x86_64 to support testing apps for large page size support.
For this reason, update Android x86_64 ELFs default max-page-size to 16384 to support both 4kB and 16kB page-size devices.
Increase max-page-size raises concerns of increased disk space and extra VMA slab memory.
In Android, RO partitions use sparse images, so that the holes on ELFs don't allocate blocks on disk; and PackageManager ensures to punch holes in ELF-paddings on the /data partition when apps are installed.
Extra VMA slab memory is addressed by the bionic loader, which extends segment VMAs to cover the gaps between consecutive segment mappings, to avoid the extra VMAs needed for the gap PROT_NONE mappings (---p). This optimization is done in the crt_pad_segment note [1] is present in the ELF.
[1] https://cs.android.com/android/platform/superproject/main/+/189e480390ef13199d59e1fb54078e8b78ea6f79:bionic/libc/arch-common/bionic/crt_pad_segment.S