Useful TSX related tools

TSX (Intel Transactional Synchronization Extension) is a hardware transactional memory extension in recent 4th generation Core Intel CPUs codenamed Haswell. For more information see http://en.wikipedia.org/wiki/Transactional_Synchronization_Extensions and http://www.intel.com/software/tsx

This package provides some tools and libraries for TSX development.

Compilation notes

You may need to update your compiler's copy of cpuid.h depending on the version. In general, it should be sufficient to simply copy the file from a newer source distribution.

For example, on Mac OS X with LLVM version 4.2 (check with cc --version), you should replace /usr/lib/clang/4.2/include/cpuid.h with the one available at https://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Headers/cpuid.h?view=co

has-tsx

Check if the current CPU supports TSX.

    % make
    % ./has-tsx
    RTM: Yes
    HLE: Yes

Emulated headers for HLE and RTM intrinsics

Headers to emulate the gcc 4.8+ and the Microsoft HLE/RTM intrinsics on older gcc compatible compilers. Plus a special header to expose the control flow of abort handlers directly using "asm goto".

rtm.h

    #include "rtm.h"        /* For gcc 4.8 use immintrin.h and -mrtm */
    ..
    if (_xbegin() == _XBEGIN_STARTED) {
            /* read lock */
            /* transaction */
            _xend();
    } else 
            /* fallback to read lock */

hle-emulation.h

Note HLE is deprecated. Please use RTM.

hle-ms.h

Provide Microsoft C compatible HLE intrinsics for gcc.

Note HLE is deprecated. Please use RTM.

rtm-goto.h

An experimential RTM intrinsics implementation that directly exposes the control flow of the abort handler. This allows to save a few instructions and may be clearer. Requires a compiler with "asm goto" support (gcc 4.7+ or some earlier RedHat gcc versions)

#include "rtm-goto.h"

XBEGIN(abort_handler);
/* Transaction */
XEND();	
return;

/* Transaction aborts come here */
unsigned status;
XFAIL_STATUS(abort_handler, status);
/* Examine status to determine abort cause */
/* Fallback path */

tsx-cpuid.h

Utility functions to check if the current CPU supports HLE or RTM from a program.

#include "tsx-cpuid.h"

init:
	if (cpu_has_rtm())
		have_rtm = 1;

lock code:
	if (have_rtm && _xbegin() == _XBEGIN_STARTED) {
		/* RTM code */
		_xend();
	} else { 
		/* fallback */
	}

ignore-xend.so

When running with the RTM enabled glibc unlocking and unlocked lock causes a general protection fault. Normal glibc ignores those. This LD_PRELOAD catches these faults and allows the buggy programs to run. May also be useful with older RTM based lock libraries.

LD_PRELOAD=/path/to/ignore-xend.so program

remove-hle.py

Remove HLE prefixes from a binary. Useful for verifying that a problem happens without HLE too. First run without -p and verify the patch sites, then use with -p binary to patch.

Warning: this can destroy a binary since there can be false positives. Always run on a backup copy.

tsx-assert.h

Normal assert does not work in TSX transaction. The assert output is an IO operation, which causes an abort so the assert gets discarded (unless it happens again when re-executed non transactionally)

This can be a curse or a blessing, but there are some situations where it is inconvenient.

tsx-assert.h provides a TSX aware assert. It only works with RTM, not with HLE. It commits the transaction before executing the assert.

#include "tsx-assert.h"

/* in transaction */
tsx_assert(condition);

Link the program with the tsx-assert.o object file

gcc ... tsx-assert.o

Based on a idea from Torvald Riegel.

glibc-tune

glibc tune allows to change the lock elision parameters in the currently running glibc.

This can be useful to experiment with elision enabled/disabled, force enable elision on glibc builds that were not built with --enable-lock-elision=yes, or tune retry parameters to improve performance on larger systems.

locks

tsxlocks is a simple library of reference TSX lock elision locks.