Rana Dasgupta wrote:
Nathan,
I was going through your patch and had a small suggestion. We had
discussed on other related threads that on Windows we wanted to use
the MSVC provided _ReadWriteBarrier intrinsic and the patch does that,
but this may not be enough. This generates no instruction, but is a
compiler fence only. x86 does not need a store fence, but for smp the
load fence can be certainly needed.
That's the assumption on Linux where in apr_memory_rw_barrier() we
insert both a compiler and an instruction fence, eg.,
apr_memory_rw_barrier()
{
...
#else
asm volatile ("lock; addl $0, 0(%%esp)":::"memory");
...
}
I agree that since there is no mfence on PIII, probably the dummy lock
is the safest option for x86 wide code. But "lock" is expensive,
specially for Pentium 4 , Centrino etc. which have the "mfence"
instruction. And this penalty on current platforms is only on Linux.
My suggestion is to do the same on Windows as well. If we need the
real fence, we need it on both....So on Windows...
On Windows in apr_thread_ext.c:
================================
#if _MSC_VER < 1400
extern void _ReadWriteBarrier();
#else
#include <intrin.h>
#endif
#pragma intrinsic (_ReadWriteBarrier)
APR_DECLARE(void) apr_memory_rw_barrier(){
#ifdef _EM64T_
// create rwfence64() in asm file port\src\thread\win\rwfence.asm
Actually MSVC (both 2003 and 2005) have intrinsics for all(?) SSE2
instructions, I found them just recently. So if you need to generate
mfence you can use _mm_mfence() [1] for it (for sfence there is
_mm_sfence() [2]). They require mmintrin.h header to me included.
[1]
ms-help://MS.VSCC.v80/MS.MSDN.v80/MS.VisualStudio.v80.en/dv_vclang/html/a9c9b42f-de9e-4374-aeb6-5f65bfb669b6.htm
[2]
ms-help://MS.VSCC.v80/MS.MSDN.v80/MS.VisualStudio.v80.en/dv_vclang/html/b6c0d18e-3628-4318-826b-45f66782e870.htm
rwfence64();
#else
__asm {lock add [esp], 0 }
#endif
_ReadWriteBarrier();
}
In port\src\thread\win\rwfence.asm:
===================================
PUBLIC rwfence64
_TEXT SEGMENT
rwfence64 PROC
mfence
PROC ENDP
TEXT ENDS
What do you think?
Thanks,
Rana
On 4/17/07, Nathan Beyer <[EMAIL PROTECTED]> wrote:
I think I have this resolved with this commit [1]. I'm now able to run
DRLVM in interpreted mode on my Quad P3 ... at least a 'Hello World'
app.
-Nathan
[1] http://svn.apache.org/viewvc?view=rev&rev=529880
On 4/18/07, Nathan Beyer <[EMAIL PROTECTED]> wrote:
> I've run into another SSE2 operation in DRLVM, this time it's in the
> hythr library, but I can't find the specific instance. According to
> GDB, it's happening in fast_thread_array() in libhythr.so.
>
> Is this from the 'apr_thread_ext.c' file? I'm going to attempt to
> modify this to be like the changes I made to the 'atomics.cpp', so
> that this can run on P3 (SSE) CPUs.
>
>
[EMAIL PROTECTED]:~/harmony/drlvm-trunk/build/lnx_ia32_gcc_debug/deploy/jdk/jre/bin$
> ./java -Xint -cp /home/nathan/workspace/helloworld/bin HelloWorld
> Illegal instruction
>
[EMAIL PROTECTED]:~/harmony/drlvm-trunk/build/lnx_ia32_gcc_debug/deploy/jdk/jre/bin$
> gdb --args ./java -Xint -cp /home/nathan/workspace/helloworld/bin
> HelloWorld
> GNU gdb 6.6-debian
> Copyright (C) 2006 Free Software Foundation, Inc.
> GDB is free software, covered by the GNU General Public License, and
you are
> welcome to change it and/or distribute copies of it under certain
conditions.
> Type "show copying" to see the conditions.
> There is absolutely no warranty for GDB. Type "show warranty" for
details.
> This GDB was configured as "i486-linux-gnu"...
> Using host libthread_db library "/lib/tls/i686/cmov/libthread_db.so.1".
> (gdb) run
> Starting program:
>
/home/nathan/harmony/drlvm-trunk/build/lnx_ia32_gcc_debug/deploy/jdk/jre/bin/java
> -Xint -cp /home/nathan/workspace/helloworld/bin HelloWorld
> [Thread debugging using libthread_db enabled]
> [New Thread -1214834000 (LWP 32414)]
> [New Thread -1215992944 (LWP 32417)]
> [New process 32414]
> [New LWP 32414]
>
> Program received signal SIGILL, Illegal instruction.
> 0xb7bc543f in fast_thread_array ()
> from
/home/nathan/harmony/drlvm-trunk/build/lnx_ia32_gcc_debug/deploy/jdk/jre/bin/libhythr.so
> (gdb) x/1i $eip
> 0xb7bc543f <fast_thread_array+510367>: mfence
> (gdb)
>
--
Gregory
