Messages in this thread | | | Date | Wed, 17 Dec 2008 12:35:59 -0800 | From | Mike Travis <> | Subject | Re: [PATCH 3/3] cpumask: add sysfs displays for configured and disabled cpu maps |
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Greg KH wrote: > On Wed, Dec 17, 2008 at 10:23:52PM +1030, Rusty Russell wrote: >> On Tuesday 16 December 2008 14:56:48 Mike Travis wrote: >>> Impact: add new functionality. >>> >>> Add sysfs files "kernel_max" and "offline" to display the max CPU index >>> allowed (NR_CPUS-1), and the map of cpus that are offline. >> I've applied this to the cpumask series, but Greg is sysfs maestro, so >> I'll await his ack (I've quoted whole thing for easy reading). > > All new sysfs files should have corrisponding Documentation/ABI files > added as well, containing all of the information in the body of this > email so that others can find it in the future in an easy manner. > > Mike, can you make this change please?
Yes, I will. > >>> Cpus can be offlined via HOTPLUG, disabled by the BIOS ACPI tables, or >>> if they exceed the number of cpus allowed by the NR_CPUS config option, >>> or the "maxcpus=NUM" kernel start parameter. >>> >>> The "possible_cpus=NUM" parameter can also extend the number of possible >>> cpus allowed, in which case the cpus not present at startup will be >>> in the offline state. (These cpus can be HOTPLUGGED ON after system >>> startup [pending a follow-on patch to provide the capability via the >>> /sys/devices/sys/cpu/cpuN/online mechanism to bring them online.]) >>> >>> By design, the "offlined cpus > possible cpus" display will always >>> use the following formats: >>> >>> * all possible cpus online: "x$" or "x-y$" >>> * some possible cpus offline: ".*,x$" or ".*,x-y$" > > Care to provide an example of what these sysfs files will actually hold? > It seems like you are craming more information than needed into a single > sysfs file.
Well, it's somewhat of a cop out as well :*). The cpus within 0 <= cpu < nr_cpu_ids are printed with a cpulist_scnprintf. This is printed for all architectures and shows primarily cpus that either have been offlined via CPU HOTPLUG or made possible by extending the number of "possible" cpus via a kernel start parameter.
Those cpus that may actually be present in the system but their index exceeds NR_CPUS/maxcpus are printed following the above and are appended to the list. If the list is non-empty, a comma is inserted first. This keeps it all within the syntax needed by cpulist_parse(). This is only done for x86 right now.
I'll put this info in the doc file. > > Oh, and state why this is really needed, as I thought we already showed > this kind of information today in the existing sysfs files, but I'm > probably wrong :)
Almost, but not quite. You can mine the syslog file to find if there's a warning message but otherwise, "extra" cpus are silently ignored.
> > thanks, > > greg k-h
Thanks! Mike
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