SMP question

Cristian Perfumo cperfumo at
Wed May 9 07:24:30 EDT 2007

Simon: (first of all: thank you for the information. As soon as we have it
working we will try that application in nofib to see what happens)
We already implemented those synchronization functions for ia64 architecture
and we have a problem related with base register (find output below).

The questions that arose:
1) What is the REG_Base?
2) Do we need it for ia64?
3) In case we need it, which machine register should we use?

Thank you very much in advance for any information.
Cristian Perfumo

== make way=thr all;
PWD = /.../ghc-6.6.1/rts
../compiler/ghc-inplace -H16m -O -optc-O2 -static -I. -#include
HCIncludes.h-fvia-C -dcmm-lint  -hisuf thr_hi -hcsuf thr_hc -osuf
-optc-DTHREADED_RTS   -c Apply.cmm -o Apply.thr_o
In file included from /.../ghc- 6.6.1/includes/Stg.h:148,

                 from /tmp/ghc1736_0/ghc1736_0.thr_hc:3:0:

     error: #error BaseReg must be in a register for THREADED_RTS
/tmp/ghc1736_0/ghc1736_0.thr_hc: In function 'stg_AP_entry':

     error: 'MainCapability' undeclared (first use in this function)

     error: (Each undeclared identifier is reported only once

     error: for each function it appears in.)
/tmp/ghc1736_0/ghc1736_0.thr_hc: In function 'stg_AP_STACK_entry':

     error: 'MainCapability' undeclared (first use in this function)
make[2]: *** [Apply.thr_o] Error 1
make[1]: *** [all] Error 1
make: *** [stage1] Error 1

On 5/9/07, Simon Marlow <simonmarhaskell at> wrote:
> Cristian Perfumo wrote:
> > Some days ago I sent an email to the list asking about the reason why I
> > couldn't run my programs with the "-Nx" RTS option even if I compiled
> > them with -threaded.
> > AH! by the way, the architecture is ia64 (Itanium).
> > Today I realized that when I ./configure, a preprocessor variable called
> > "NOSMP" is defined and it disallows the multiple OS threads (the -Nx
> > option).
> > Looking a bit deeper I figured out that there's no Itanium version for
> > the functions xchg (exchange), cas (compare-and-swap) and write_barrier
> > in the header file SMP.h (includes/SMP.h) so there's no way that the
> > holy -N option is available.
> > My question is: is it enough to implement xchg, cas and write_barrier
> > for ia64 to make multiple OSthreads available on ia64? If not, what else
> > should be implemented/changed?
> Yes, that should be enough.  The main concern is that on architectures
> that
> don't have strong memory ordering, that the thunk update sequence is
> safe.  See
> section 3.3:
> At the moment the update code contains a memory barrier, which compiles to
> nothing on x86/x86_64 (see SMP.h:write_barrier()).  You should check that
> this
> doesn't impose a significant performance penalty on ia64: try one of the
> benchmarks that does a lot of updates (e.g. nofib/imaginary/exp3_8) with
> and
> without -threaded.
> Cheers,
>         Simon
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