Messages in this thread | | | Subject | Re: [PATCH v2 17/23] x86/resctrl: Abstract __rmid_read() | From | James Morse <> | Date | Wed, 27 Oct 2021 17:50:31 +0100 |
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Hi Reinette, Babu,
On 20/10/2021 21:28, Reinette Chatre wrote: > On 10/20/2021 12:22 PM, Babu Moger wrote: >> On 10/20/21 1:15 PM, Reinette Chatre wrote: >>> On 10/19/2021 4:20 PM, Babu Moger wrote: >>>> On 10/1/21 11:02 AM, James Morse wrote: >>>>> __rmid_read() selects the specified eventid and returns the counter >>>>> value from the msr. The error handling is architecture specific, and >>>>> handled by the callers, rdtgroup_mondata_show() and __mon_event_count(). >>>>> >>>>> Error handling should be handled by architecture specific code, as >>>>> a different architecture may have different requirements. MPAM's >>>>> counters can report that they are 'not ready', requiring a second >>>>> read after a short delay. This should be hidden from resctrl. >>>>> >>>>> Make __rmid_read() the architecture specific function for reading >>>>> a counter. Rename it resctrl_arch_rmid_read() and move the error >>>>> handling into it.
>>>>> diff --git a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c >>>>> b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c >>>>> index 25baacd331e0..c8ca7184c6d9 100644 >>>>> --- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c >>>>> +++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c >>>>> @@ -579,9 +579,9 @@ int rdtgroup_mondata_show(struct seq_file *m, void >>>>> *arg) >>>>> mon_event_read(&rr, r, d, rdtgrp, evtid, false); >>>>> - if (rr.val & RMID_VAL_ERROR) >>>>> + if (rr.err == -EIO) >>>>> seq_puts(m, "Error\n"); >>>>> - else if (rr.val & RMID_VAL_UNAVAIL) >>>>> + else if (rr.err == -EINVAL) >>>>> seq_puts(m, "Unavailable\n"); >>>>> else >>>>> seq_printf(m, "%llu\n", rr.val * hw_res->mon_scale); >>>> >>>> This patch breaks the earlier fix >>>> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit.kernel.org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Ftorvalds%2Flinux.git%2Fcommit%2F%3Fh%3Dv5.15-rc6%26id%3D064855a69003c24bd6b473b367d364e418c57625&data=04%7C01%7Cbabu.moger%40amd.com%7C85219a5827114935cdaa08d993f59fa0%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637703505420472920%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=yP8awDgGGZ%2BWj5ZItdTNJItTVuK828yGnibwq%2BrVaf0%3D&reserved=0
Aha!
>>>> When the user reads the events on the default monitoring group with >>>> multiple subgroups, the events on all subgroups are consolidated >>>> together. In case if the last rmid read was resulted in error then whole >>>> group will be reported as error. The err field needs to be cleared. >>>> >>>> Please add this patch to clear the error.
>>> Good catch, thank you. >>> >>> Even so, I do not think mon_event_count()'s usage of __mon_event_count() >>> was taken into account by this patch and needs a bigger rework than the >>> above fixup. For example, if I understand correctly ret_val is the error >>> and rr->val no longer expected to contain the error after this patch. So >>> keeping that assignment to rr->val is not correct. >> >> Yes. You are right. rr->val is not expected to contain the error. >> Hopefully, this should help.
> Yes, this looks good. If the first __mon_event_count() succeeds but a following one fails > then the data still needs to be reported so the error code needs to be fixed up afterwards > and cannot be done inside __mon_event_count(). Thank you very much.
Thanks both! I should have worked this out when splitting msr_val into two values, which end up getting set the same.
I think the 'Unavailable' issue is subtle enough that it deserves a block comment. I've replaced the rr->val chunk with: | /* | * __mon_event_count() calls for newly created monitor groups may | * report -EINVAL/Unavailable if the monitor hasn't seen any traffic. | * If the first call for the control group succeed, discard any error | * set by reads of monitor groups. | */ | if (ret_val == 0) | rr->err = 0;
Thanks.
James
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