Messages in this thread | | | Date | Mon, 22 Nov 2010 15:13:24 -0500 (EST) | From | Len Brown <> | Subject | Re: [PATCH RESEND] tools: add power/x86/x86_energy_perf_policy to program MSR_IA32_ENERGY_PERF_BIAS |
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Hi Andy,
Thank you for the review!
responses below.
> > +install : > > + install x86_energy_perf_policy /usr/bin/x86_energy_perf_policy > > It's not clear to me how this Makefile ensures it's only > build on x86. > > If someone on another architecture does a full tools build > in the future (I think that is not wired up yet, but should > eventually) such a mechanism would be needed.
Per the comments from Andrew and others, the concept of a "full tools build" doesn't actually exit (yet).
So I guess the only assurance that somebody not on x86 would run make in this directory this utility lives in tools/power/x86/
Note that there are other utilities under tools which have no Makefile at all...
> ...I would prefer a manpage
I'll be happy to write a manpage. Is there good example I should follow?
> > +cmdline(int argc, char **argv) { > > No type?
okay, now void.
> > + while ((opt = getopt(argc, argv, "+rvc:")) != -1) { > > Maybe it's me, but I prefer having long options too (getopt_long) > These are easier to memorize.
I'm not inclined to bother, as the use-case for this utility is to be invoked by another program, and the options available are really there just for verification/debugging, and don't really merit being memorized by a human after that task.
> An obvious improvement would be to put the exit() into usage()
done.
> > + new_bias = atoll(argv[optind]); > > If you used strtoull() you could actually check if the input > is really a number (end == argv[optind])
done.
> > + asm("cpuid" : "=a" (max_level), "=b" (ebx), "=c" (ecx), > > + "=d" (edx) : "a" (0)); > > Strictly for 386/early 486 you would need to check if cpuid > is available using pushf too. Perhaps it's safer to use cpuinfo
Meh, maybe simpler to crash on 486 and earlier?:-) I'm not fond of parsing /proc/cpuinfo.
> > +check_dev_msr() { > > Return type missing again
routine deleted.
> > + struct stat sb; > > + > > + if (stat("/dev/cpu/0/msr", &sb)) { > > + printf("no /dev/cpu/0/msr\n"); > > This will fail if we eventually implement cpu 0 hotplug... > Better readdir or similar.
simpler to delete check_dev_msr() and stumble forward assuming /dev/cpu/*/msr exists, and print a message and exit if it doesn't.
> > + printf("Try \"# modprobe msr\"\n"); > > + exit(-5); > > Again -5 is unusual.
okay, I canged all the exits to 1.
> > + sprintf(msr_path, "/dev/cpu/%d/msr", cpu); > > + fd = open(msr_path, O_RDONLY); > > + if (fd < 0) { > > + perror(msr_path); > > + exit(-1); > > This should be a soft error because the CPU can go away > any time.
In the highly unlikely scenario that somebody uses the -r option to excerise the read-only code, and simultaneously invokes and completes a cpu hot remove during the execution of this utility, I think the utility exiting is just as useful, and less complicated, than handling soft error. Since in either case, the user would probably simply re-invoke the utility to see what the current state of the settled machine is.
> > +/* > > + * run func() on every cpu in /dev/cpu > > + */ ... > > + fp = fopen(proc_stat, "r"); > > Using /proc/stat to get the number of CPUs is unusual > and you don't handle holes in the cpu numbers which > can happen due to hotplug.
The code does handle holes in cpu number namespace.
The "num_cpus" variable was a hold-over from an older version that did not, and so I've deleted it.
> I would just readdir or fnmatch the MSR /dev/cpu/* directories.
I used to do that, but Arjan convinced me to use /proc/stat. turbostat, rdmsr, and wrmsr all use /proc/stat.
thanks, -Len Brown, Intel Open Source Technology Center
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