David,
Thanks for the review.
On 5/5/2014 7:59 PM, David Holmes wrote:
Hi Yumin,
For something that only addresses one platform this adds a lot of
platform specific code to a bunch of shared files. Are there plans to
extend this to other platforms? Otherwise can we make this more
platform agnostic? Perhaps move the os specific code to the os class?
Seems the changes in filemap.cpp and metaspace.cpp could easily be
factored into an os method that returns a boolean to indicate whether
there is a fixed mapping.
Let me rethink and reorganize the code.
And perhaps define set_static_shared_space in the os class and always
expose it via jni.cpp. Actually, why are we exposing this via jni.cpp
rather than jvm.cpp? This is not part of the JNI interface to the VM.
I think I can use JVM_LEAF, other entries all call to get current
JavaThread which is not available at the time this function called since
VM is not init'ed. But using this entry is dangerous too.
verify_stack_alignment() will be called in JVM_LEAF_BASE, it won't have
effect since it is empty function for debug version. It may become
problematic in future I think, so i decided to have a plain JNI function
so put it in jni.cpp. This function is more like a private function.
Thanks
Yumin
Thanks,
David
On 6/05/2014 9:15 AM, Yumin Qi wrote:
Hi, Please have codereview for
8042243: Map shared archive to preallocated static address
webrev: http://cr.openjdk.java.net/~minqi/8042243/webrev00/
bug: https://bugs.openjdk.java.net/browse/JDK-8042243
Summary: Mapping shared archive (jsa) some time fail due to ASLR
(Address space layout randomization) on 32bit Linux platforms. To solve
we come up with mapping shared archive to preallocated static space
since with Linux and the GCC compiler, the BSS section in the main
executable is not randomized, instead, the variable address in the BSS
section is fixed at build time. The tests also showed the extra 32M
space will NOT affect java memory setting though it seems 32M virtual
address space always allocated no matter it is used or not (If
-XX:ShareBaseAddress supply alternative address for dumping, the static
address will be ignored.) Note the changes is for 32 bit Linux only.
Tests: JPRT, manual test for archive sharing.
Thanks
Yumin
