RTM disabled for Linux on PPC64 LE
Gustavo Romero
gromero at linux.vnet.ibm.com
Mon Feb 15 14:22:38 UTC 2016
Hello Martin,
Thank you for your reply.
The problematic behavior of syscalls has been addressed since kernel 4.2
(already present in, por instance, Ubuntu 15.10 and 16.04):
https://goo.gl/d80xAJ
I'm taking a closer look at the RTM tests and I'll make additional
experiments as you suggested.
So far I enabled RTM for Linux on ppc64le and there is no regression in
the RTM test suite. I'm using kernel 4.2.0.
The following patch was applied to
http://hg.openjdk.java.net/jdk9/jdk9/hotspot, 5d17092b6917+ tip, and I
used the (major + minor) version to enable RTM as you said:
# HG changeset patch
# User gromero
# Date 1455540780 7200
# Mon Feb 15 10:53:00 2016 -0200
# Node ID 0e9540f2156c4c4d7d8215eb89109ff81be82f58
# Parent 5d17092b691720d71f06360fb0cc183fe2877faa
Enable RTM for Linux on PPC64 LE
Enable RTM for Linux kernel version equal or above 4.2, since the
problematic behavior of performing a syscall from within transaction
which could lead to unpredictable results has been addressed. Please,
refer to https://goo.gl/fi4tjC
diff --git a/src/cpu/ppc/vm/globalDefinitions_ppc.hpp b/src/cpu/ppc/vm/globalDefinitions_ppc.hpp
--- a/src/cpu/ppc/vm/globalDefinitions_ppc.hpp
+++ b/src/cpu/ppc/vm/globalDefinitions_ppc.hpp
@@ -52,4 +52,9 @@
#define INCLUDE_RTM_OPT 1
#endif
+// Enable RTM experimental support for Linux.
+#if defined(COMPILER2) && defined(linux)
+#define INCLUDE_RTM_OPT 1
+#endif
+
#endif // CPU_PPC_VM_GLOBALDEFINITIONS_PPC_HPP
diff --git a/src/cpu/ppc/vm/vm_version_ppc.cpp b/src/cpu/ppc/vm/vm_version_ppc.cpp
--- a/src/cpu/ppc/vm/vm_version_ppc.cpp
+++ b/src/cpu/ppc/vm/vm_version_ppc.cpp
@@ -255,7 +255,12 @@
}
#endif
#ifdef linux
- // TODO: check kernel version (we currently have too old versions only)
+ // At least Linux kernel 4.2, as the problematic behavior of syscalls
+ // being called from within a transaction has been addressed.
+ // Please, refer to commit 4b4fadba057c1af7689fc8fa182b13baL7
+ if (os::Linux::os_version() >= 0x040200) {
+ os_too_old = false;
+ }
#endif
if (os_too_old) {
vm_exit_during_initialization("RTM is not supported on this OS version.");
diff --git a/src/os/linux/vm/os_linux.cpp b/src/os/linux/vm/os_linux.cpp
--- a/src/os/linux/vm/os_linux.cpp
+++ b/src/os/linux/vm/os_linux.cpp
@@ -135,6 +135,7 @@
int os::Linux::_page_size = -1;
const int os::Linux::_vm_default_page_size = (8 * K);
bool os::Linux::_supports_fast_thread_cpu_time = false;
+uint32_t os::Linux::_os_version = 0;
const char * os::Linux::_glibc_version = NULL;
const char * os::Linux::_libpthread_version = NULL;
pthread_condattr_t os::Linux::_condattr[1];
@@ -4332,6 +4333,31 @@
return (tp.tv_sec * NANOSECS_PER_SEC) + tp.tv_nsec;
}
+void os::Linux::initialize_os_info() {
+ assert(_os_version == 0, "OS info already initialized");
+
+ struct utsname _uname;
+
+ uint32_t major;
+ uint32_t minor;
+ uint32_t fix;
+
+ uname(&_uname); // Not sure yet how to bail out if ret == -1
+ sscanf(_uname.release,"%d.%d.%d", &major,
+ &minor,
+ &fix );
+
+ _os_version = (major << 16) |
+ (minor << 8 ) |
+ (fix << 0 ) ;
+}
+
+uint32_t os::Linux::os_version() {
+ assert(_os_version != 0, "not initialized");
+ return _os_version;
+}
+
+
/////
// glibc on Linux platform uses non-documented flag
// to indicate, that some special sort of signal
@@ -4552,6 +4578,8 @@
}
init_page_sizes((size_t) Linux::page_size());
+ Linux::initialize_os_info();
+
Linux::initialize_system_info();
// main_thread points to the aboriginal thread
diff --git a/src/os/linux/vm/os_linux.hpp b/src/os/linux/vm/os_linux.hpp
--- a/src/os/linux/vm/os_linux.hpp
+++ b/src/os/linux/vm/os_linux.hpp
@@ -56,6 +56,12 @@
static GrowableArray<int>* _cpu_to_node;
+ // Ox00AABBCC
+ // AA, Major Version
+ // BB, Minor Version
+ // CC, Fix Version
+ static uint32_t _os_version;
+
protected:
static julong _physical_memory;
@@ -198,6 +204,9 @@
static jlong fast_thread_cpu_time(clockid_t clockid);
+ static void initialize_os_info();
+ static uint32_t os_version();
+
// pthread_cond clock suppport
private:
static pthread_condattr_t _condattr[1];
Should I use any test suite besides the jtreg suite already present
in the Hotspot forest?
Best Regards,
Gustavo
On 12-02-2016 12:52, Doerr, Martin wrote:
> Hi Gustavo,
>
> the reason why we disabled RTM for linux on PPC64 (big or little endian) was the problematic behavior of syscalls.
> The old version of the document
> www.kernel.org/doc/Documentation/powerpc/transactional_memory.txt
> said:
> “Performing syscalls from within transaction is not recommended, and can lead to unpredictable results.“
>
> Transactions need to either pass completely or roll back completely without disturbing side effects of partially executed syscalls.
> We rely on the kernel to abort transactions if necessary.
>
> The document has changed and it may possibly work with a new linux kernel.
> However, we don't have such a new kernel, yet. So we can't test it at the moment.
> I don't know which kernel version exactly contains the change. I guess this exact version number (major + minor) should be used for enabling RTM.
>
> I haven't looked into the tests, yet. There may be a need for additional adaptations and fixes.
>
> We appreciate if you make experiments and/or contributions.
>
> Thanks and best regards,
> Martin
>
>
> -----Original Message-----
> From: ppc-aix-port-dev [mailto:ppc-aix-port-dev-bounces at openjdk.java.net] On Behalf Of Gustavo Romero
> Sent: Freitag, 12. Februar 2016 14:45
> To: hotspot-dev at openjdk.java.net; ppc-aix-port-dev at openjdk.java.net
> Subject: RTM disabled for Linux on PPC64 LE
> Importance: High
>
> Hi,
> As of now (tip 1922:be58b02c11f9, jdk9/jdk9 repo) Hotspot build for Linux on ppc64le of fails due to a simple uninitialized variable error:
>
> hotspot/src/share/vm/ci/ciMethodData.hpp:585:100: error: ‘data’ may be used uninitialized in this function
> hotspot/src/cpu/ppc/vm/c1_LIRAssembler_ppc.cpp:2408:78: error: ‘md’ may be used uninitialized in this function
>
> So this straightforward patch solves the issue:
> diff -r 534c50395957 src/cpu/ppc/vm/c1_LIRAssembler_ppc.cpp
> --- a/src/cpu/ppc/vm/c1_LIRAssembler_ppc.cpp Thu Jan 28 15:42:23 2016 -0800
> +++ b/src/cpu/ppc/vm/c1_LIRAssembler_ppc.cpp Mon Feb 08 17:13:14 2016 -0200
> @@ -2321,8 +2321,8 @@
> if (reg_conflict) { obj = dst; }
> }
> - ciMethodData* md;
> - ciProfileData* data;
> + ciMethodData* md = NULL;
> + ciProfileData* data = NULL;
> int mdo_offset_bias = 0; compiler/rtm
> if (should_profile) {
> ciMethod* method = op->profiled_method();
>
> However, after the build, I realized that RTM is still disabled for Linux on ppc64le, failing 25 tests on compiler/rtm suite:
>
> http://hastebin.com/raw/ohoxiwaqih
>
> Hence after applying the following patches that enable RTM for Linux on ppc64le:
>
> diff -r 266fa9bb5297 src/cpu/ppc/vm/vm_version_ppc.cpp
> --- a/src/cpu/ppc/vm/vm_version_ppc.cpp Thu Feb 04 16:48:39 2016 -0800
> +++ b/src/cpu/ppc/vm/vm_version_ppc.cpp Fri Feb 12 10:55:46 2016 -0200
> @@ -255,7 +255,9 @@
> }
> #endif
> #ifdef linux
> - // TODO: check kernel version (we currently have too old versions only)
> + if (os::Linux::os_version() >= 4) { // at least Linux kernel version 4
> + os_too_old = false;
> + }
> #endif
> if (os_too_old) {
> vm_exit_during_initialization("RTM is not supported on this OS version.");
>
>
> diff -r 266fa9bb5297 src/os/linux/vm/os_linux.cpp
> --- a/src/os/linux/vm/os_linux.cpp Thu Feb 04 16:48:39 2016 -0800
> +++ b/src/os/linux/vm/os_linux.cpp Fri Feb 12 10:58:10 2016 -0200
> @@ -135,6 +135,7 @@
> int os::Linux::_page_size = -1;
> const int os::Linux::_vm_default_page_size = (8 * K);
> bool os::Linux::_supports_fast_thread_cpu_time = false;
> +uint32_t os::Linux::_os_version = 0;
> const char * os::Linux::_glibc_version = NULL;
> const char * os::Linux::_libpthread_version = NULL;
> pthread_condattr_t os::Linux::_condattr[1];
> @@ -4332,6 +4333,21 @@
> return (tp.tv_sec * NANOSECS_PER_SEC) + tp.tv_nsec;
> }
> +void os::Linux::initialize_os_info() {
> + assert(_os_version == 0, "OS info already initialized");
> +
> + struct utsname _uname;
> + + uname(&_uname); // Not sure yet how deal if ret == -1
> + _os_version = atoi(_uname.release);
> +}
> +
> +uint32_t os::Linux::os_version() {
> + assert(_os_version != 0, "not initialized");
> + return _os_version;
> +}
> +
> +
> /////
> // glibc on Linux platform uses non-documented flag
> // to indicate, that some special sort of signal
> @@ -4553,6 +4569,7 @@
> init_page_sizes((size_t) Linux::page_size());
> Linux::initialize_system_info();
> + Linux::initialize_os_info();
> // main_thread points to the aboriginal thread
> Linux::_main_thread = pthread_self();
>
>
> diff -r 266fa9bb5297 src/os/linux/vm/os_linux.hpp
> --- a/src/os/linux/vm/os_linux.hpp Thu Feb 04 16:48:39 2016 -0800
> +++ b/src/os/linux/vm/os_linux.hpp Fri Feb 12 10:59:01 2016 -0200
> @@ -55,7 +55,7 @@
> static bool _supports_fast_thread_cpu_time;
> static GrowableArray<int>* _cpu_to_node;
> -
> + static uint32_t _os_version; protected:
> static julong _physical_memory;
> @@ -198,6 +198,9 @@
> static jlong fast_thread_cpu_time(clockid_t clockid);
> + static void initialize_os_info();
> + static uint32_t os_version(); +
> // pthread_cond clock suppport
> private:
> static pthread_condattr_t _condattr[1];
>
>
> 23 tests are now passing: http://hastebin.com/raw/oyicagusod
>
> Is there a reason to let RTM disabled for Linux on ppc64le by now? Could somebody explain what is currently missing on PPC64 LE RTM implementation in order to make all RTM tests pass?
>
> Thank you.
>
> Regards,
> --
> Gustavo Romero
>
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