Ok. We'll rely on your patches. :-)
On Feb 28, 2012, at 11:00 AM, Leif Lindholm wrote: > We'd need a few ifdefs, effectively. > > One on the dmb/mcr and one on the 64-bit, depending on v6k or higher. > > This would provide ARMv6 support only though - ARMv5 or earlier (like debian > "armel") will still miss out. > >> -----Original Message----- >> From: devel-boun...@open-mpi.org [mailto:devel-boun...@open-mpi.org] On >> Behalf Of Jeffrey Squyres >> Sent: 28 February 2012 14:10 >> To: Leif Lindholm >> Cc: Open MPI Developers; Ron Broberg >> Subject: Re: [OMPI devel] Compiling OpenMPI 1.5.4 on Debian 6 qemu >> arm6l >> >> Are there any changes we need to make to OMPI? >> >> >> On Feb 28, 2012, at 7:50 AM, Leif Lindholm wrote: >> >>> Hi Ron, >>> >>> Excellent work! Indeed - simply dropping the DMBs can lead to memory >> consistency issues even on ARMv6. >>> >>> The architectural semantics for memory barriers exist in ARMv6 though >> - they just weren't given dedicated mnemonics. >>> What you could do is to simply replace the inline "dmb" sequences >> with inline cp15 operations: >>> - "MCR p15, 0, r0, c7, c10, 5" >>> (the 'r0' is an encoding artefact and doesn't affect the register >>> contents) >>> >>> LDREXD/STREXD weren't part of the ARMv6 base architecture, although >> they are supported by the 1176 which is used in the Raspberry PI. If >> your tools support detecting/building for extension subarchitecture >> ARMv6k (supported by 1176), you can actually keep the 64-bit atomics >> in. >>> >>> Best Regards, >>> >>> Leif >>> >>> References: >>> >> http://infocenter.arm.com/help/topic/com.arm.doc.ddi0301h/Babfdddg.html >>> >> http://infocenter.arm.com/help/topic/com.arm.doc.ddi0301h/Babhejba.html >>> >>>> -----Original Message----- >>>> From: Jeffrey Squyres [mailto:jsquy...@cisco.com] >>>> Sent: 28 February 2012 12:30 >>>> To: Ron Broberg; Open MPI Developers >>>> Cc: Leif Lindholm >>>> Subject: Re: [OMPI devel] Compiling OpenMPI 1.5.4 on Debian 6 qemu >>>> arm6l >>>> >>>> Ron -- Many thanks! >>>> >>>> Leif -- can you comment on this? (yes, I'm passing the buck to our >> ARM >>>> Open MPI representative :-) ) >>>> >>>> >>>> On Feb 26, 2012, at 1:22 PM, Ron Broberg wrote: >>>> >>>>> I would like to report the following information regarding >> compiling >>>> OpenMPI on Debian ARMv6. I won't submit this as a patch because I >> don't >>>> believe that "delete all 'dmb' instructions" can be considered a >> well >>>> developed patch. But this information may be of use to someone down >> the >>>> line. >>>>> >>>>> I was able to compile the upstream openmpi-1.5.4 distribution on a >>>> Debian6 armv6l qemu emulation. >>>>> http://www.open-mpi.org/software/ompi/v1.4/downloads/openmpi- >>>> 1.4.5.tar.bz2 >>>>> >>>>> >>>>> You have to make 3 changes to the package >>>>> 1) Delete all references to the RISC instruction 'dmb' >>>>> 2) Modify the 'configure' file to include an 'armv6' option >>>>> 3) Compile with CFLAGS=-march=armv6 >>>>> >>>>> ## 1) make the following edits to these three files >>>>> ./opal/asm/generated/atomic-local.s >>>>> delete all dmb instructions >>>>> ./opal/asm/base/ARM.asm >>>>> delete all dmb instructions >>>>> ./opal/include/opal/sys/arm/atomic.h >>>>> change the lines: >>>>> #if OPAL_WANT_SMP_LOCKS >>>>> #define MB() __asm__ __volatile__ ("dmb" : : : "memory") >>>>> #define RMB() __asm__ __volatile__ ("dmb" : : : "memory") >>>>> #define WMB() __asm__ __volatile__ ("dmb" : : : "memory") >>>>> #else >>>>> #define MB() >>>>> #define RMB() >>>>> #define WMB() >>>>> #endif >>>>> >>>>> to read: >>>>> #define MB() >>>>> #define RMB() >>>>> #define WMB() >>>>> >>>>> ## 2) add the following to the 'configure' file at line 26946 of >>>> 171183 >>>>> goto line 26946, there should be an 'alpha-' section above and an >>>> 'armv7' below >>>>> insert the following >>>>> armv6*) >>>>> ompi_cv_asm_arch="ARM" >>>>> OPAL_ASM_SUPPORT_64BIT=0 >>>>> OMPI_GCC_INLINE_ASSIGN='"mov %0, #0" : "=&r"(ret)' >>>>> ;; >>>>> >>>>> ## 3) compile and install with the following CFLAGS >>>>> CFLAGS=-march=armv6 >>>>> ./configure CFLAGS=-march=armv6 >>>>> make >>>>> sudo make install >>>>> >>>>> more information about my build at >>>>> http://rhinohide.wordpress.com/2012/02/26/openmpi-on-raspberry-pi/ >>>>> >>>>> >>>>> _______________________________________________ >>>>> devel mailing list >>>>> de...@open-mpi.org >>>>> http://www.open-mpi.org/mailman/listinfo.cgi/devel >>>> >>>> >>>> -- >>>> Jeff Squyres >>>> jsquy...@cisco.com >>>> For corporate legal information go to: >>>> http://www.cisco.com/web/about/doing_business/legal/cri/ >>>> >>> >>> >>> -- IMPORTANT NOTICE: The contents of this email and any attachments >> are confidential and may also be privileged. If you are not the >> intended recipient, please notify the sender immediately and do not >> disclose the contents to any other person, use it for any purpose, or >> store or copy the information in any medium. Thank you. >>> >> >> >> -- >> Jeff Squyres >> jsquy...@cisco.com >> For corporate legal information go to: >> http://www.cisco.com/web/about/doing_business/legal/cri/ >> >> >> _______________________________________________ >> devel mailing list >> de...@open-mpi.org >> http://www.open-mpi.org/mailman/listinfo.cgi/devel > > > -- IMPORTANT NOTICE: The contents of this email and any attachments are > confidential and may also be privileged. If you are not the intended > recipient, please notify the sender immediately and do not disclose the > contents to any other person, use it for any purpose, or store or copy the > information in any medium. Thank you. > -- Jeff Squyres jsquy...@cisco.com For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/
