On Mon, Jul 08, 2013 at 01:34:25PM -0400, Camm Maguire wrote: > Greetings! Can anyone provide temporary access to an alpha to chase > down a quick bug on gcl?
I presume you got access to Bill's Alpha. I noted in the gcl 2.6.7+dfsga-35 changelog that gcl is now compiled with -O0 on Alpha. I was wondering what is the reason for that. It's just that -O0 has a substantial impact on speed on Alpha, it being a register based RISC arch. At -O0 all accesses to local variables are forced to be off the stack thus involve memory accesses. Optimisation at -O1 allows local variables to be held in CPU registers and provides a substantial speed increase over -O0. Building acl2 now is horrendously slow and the last build got killed by the sbuild watchdog when it did not observe any new output on the log for 150 minutes. And that was on the fastest Alpha we have as a buildd! I suspect it was not a real build failure as the prior version (6.2-5) did actually build to completion but I was not fast enough to upload it before 6.2-6 came along. Also the log file never made it to debian-ports as it exceeded the buildd site's limits on email length (even after compression). I also noted in the kernel log reports of misaligned memory accesses executed by gcl. At best these only represented an inefficiency as the misaligned memory access traps to the kernel and the kernel completes the memory access. Sometimes though they indicate real bugs in the sofware. I have seen gcc "optimise" a misaligned memory access to generate code that only works if the memory access is correctly aligned, presumably because misaligned memory accesses are undefined behaviour under the C standards which permits gcc to do whatever it damn well likes. So it might be worthwhile exploring these misaligned memory accesses more closely. On the other hand I would not be surprised if no one is running these software packages on Alpha so it may not be worth putting too much time into this. Cheers Michael. -- To UNSUBSCRIBE, email to debian-alpha-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/20130806085454.GA12868@omega