Messages in this thread | | | Date | Mon, 9 Jan 2023 15:43:11 -0800 | Subject | Re: [PATCH v11 04/13] x86/cpufeatures: Add Bandwidth Monitoring Event Configuration feature flag | From | Reinette Chatre <> |
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Hi Boris and Tony,
On 1/9/2023 1:39 PM, Borislav Petkov wrote: > On Mon, Jan 09, 2023 at 09:25:32PM +0000, Luck, Tony wrote: >> It feels like the old "rule" was "make it visible in /proc/cpuid" unless there was some >> good reason NOT to do it. But that has resulted in the "flags" line getting ridiculously >> long and hard for humans to read (141 fields with 926 bytes on my Skylake, >> more on more modern CPUs). > > Yap, imagine every possible CPUID bit were in there... > >> I don't know if we'd break anything if we dropped: >> >> cat_l3 cdp_l3 mba cqm_llc cqm_occup_llc cqm_mbm_total cqm_mbm_local >> >> from /proc/cpuinfo. > > I wouldn't mind if we remove them from cpuinfo, frankly.
I am afraid that I am not aware of all the resctrl user space apps and tools being used.
I did take a quick look at intel-cmt-cat that has an active user base and from what I can tell it uses /proc/cpuinfo to learn some capabilities:
Example of looking for "cqm" (although "cqm" is not in Tony's list): https://github.com/intel/intel-cmt-cat/blob/master/lib/os_cap.c#L420
Example of looking for "cdp_l3": https://github.com/intel/intel-cmt-cat/blob/master/lib/os_cap.c#L520
Example of looking for "cdp_l2": https://github.com/intel/intel-cmt-cat/blob/master/lib/os_cap.c#L564
> >> Perhaps the "rule" should be written in Documentation/{somewhere}? > > This started documenting it: > > Documentation/x86/cpuinfo.rst >
We could make a rule that no more resctrl related features are added to cpuinfo but I am hesitant to remove the ones that are already there.
Reinette
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