Messages in this thread | | | Subject | Re: [PATCH 2/2] perf tools: Improve IBS error handling | From | kajoljain <> | Date | Wed, 8 Dec 2021 12:03:01 +0530 |
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On 11/30/21 3:39 AM, Kim Phillips wrote: > On 11/24/21 2:00 AM, kajoljain wrote: >> On 11/23/21 8:55 PM, Kim Phillips wrote: >>> On 11/23/21 2:40 AM, kajoljain wrote: >>>> On 10/8/21 12:47 AM, Kim Phillips wrote: >>>>> On 10/7/21 12:28 PM, Jiri Olsa wrote: >>>>>> On Mon, Oct 04, 2021 at 04:41:14PM -0500, Kim Phillips wrote: >>>>>>> --- >>>>>>> tools/perf/util/evsel.c | 24 ++++++++++++++++++++++++ >>>>>>> 1 file changed, 24 insertions(+) >>>>>>> >>>>>>> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c >>>>>>> index b915840690d4..f8a9cbd99314 100644 >>>>>>> --- a/tools/perf/util/evsel.c >>>>>>> +++ b/tools/perf/util/evsel.c >>>>>>> @@ -2743,9 +2743,22 @@ static bool find_process(const char *name) >>>>>>> return ret ? false : true; >>>>>>> } >>>>>>> +static bool is_amd(const char *arch, const char *cpuid) >>>>>>> +{ >>>>>>> + return arch && !strcmp("x86", arch) && cpuid && >>>>>>> strstarts(cpuid, >>>>>>> "AuthenticAMD"); >>>>>>> +} >>>>>>> + >>>>>>> +static bool is_amd_ibs(struct evsel *evsel) >>>>>>> +{ >>>>>>> + return evsel->core.attr.precise_ip || !strncmp(evsel->pmu_name, >>>>>>> "ibs", 3); >>>>>>> +} >>>>>>> + >>>>>>> int evsel__open_strerror(struct evsel *evsel, struct target >>>>>>> *target, >>>>>>> int err, char *msg, size_t size) >>>>>>> { >>>>>>> + struct perf_env *env = evsel__env(evsel); >>>>>>> + const char *arch = perf_env__arch(env); >>>>>>> + const char *cpuid = perf_env__cpuid(env); >>>>>>> char sbuf[STRERR_BUFSIZE]; >>>>>>> int printed = 0, enforced = 0; >>>>>>> @@ -2841,6 +2854,17 @@ int evsel__open_strerror(struct evsel >>>>>>> *evsel, struct target *target, >>>>>>> return scnprintf(msg, size, "wrong clockid (%d).", >>>>>>> clockid); >>>>>>> if (perf_missing_features.aux_output) >>>>>>> return scnprintf(msg, size, "The 'aux_output' >>>>>>> feature >>>>>>> is not supported, update the kernel."); >>>>>>> + if (is_amd(arch, cpuid)) { >>>>>>> + if (is_amd_ibs(evsel)) { >>>>>> >>>>>> would single 'is_amd_ibs' call be better? checking on both amd and >>>>>> ibs >>>>> >>>>> Good suggestion. If you look at the later patch in the >>>>> BRS series, I have rewritten it to add the new >>>>> AMD PMU like so: >>>>> >>>>> if (is_amd()) { >>>>> if (is_amd_ibs()) { >>>>> if (evsel->this) >>>>> return >>>>> if (evsel->that) >>>>> return >>>>> } >>>>> + if (is_amd_brs()) { >>>>> + if (evsel->this) >>>>> + return >>>>> + if (evsel->that) >>>>> + return >>>>> + } >>>>> } >>>> >>>> Hi Kim, >>>> From my point of view, it won't be a good idea of adding so many >>>> checks in common function definition itself. >>>> Can you just create a check to see if its amd machine and then add a >>>> function call which will handle all four conditions together? >>>> >>>> which is basically for: >>>> >>>> + if (is_amd(arch, cpuid)) { >>>> + if (is_amd_ibs(evsel)) { >>>> + if (evsel->core.attr.exclude_kernel) >>>> + return scnprintf(msg, size, >>>> + "AMD IBS can't exclude kernel events. Try running at a higher >>>> privilege level."); >>>> + if (!evsel->core.system_wide) >>>> + return scnprintf(msg, size, >>>> + "AMD IBS may only be available in system-wide/per-cpu mode. Try >>>> using >>>> -a, or -C and workload affinity"); >>>> + } >>>> >>>> and this: >>>> >>>> + if (is_amd_brs(evsel)) { >>>> + if (evsel->core.attr.freq) >>>> + return scnprintf(msg, size, >>>> + "AMD Branch Sampling does not support frequency mode sampling, >>>> must >>>> pass a fixed sampling period via -c option or >>>> cpu/branch-brs,period=xxxx/."); >>>> + /* another reason is that the period is too small */ >>>> + return scnprintf(msg, size, >>>> + "AMD Branch Sampling does not support sampling period smaller than >>>> what is reported in /sys/devices/cpu/caps/branches."); >>>> + } >>> >>> IIRC, I tried something like that but carrying the >>> >>> >>> struct target *target, int err, char *msg, size_t size >>> >>> parameters made things worse. >>> >>>> So, incase we are in amd machine, common function evsel__open_strerror >>>> will call function may be something like amd_evesel_open_strerror_check >>>> which will look for both ibs and brs conditions and return >>>> corresponding >>>> error statement. >>> >>> The vast majority of decisions made by evsel__open_strerror are >>> going to be common across most arch/uarches. AMD has only these >>> two pesky exceptions to the rule and therefore IMO it's ok >>> to have them inline with the common function, since the decisions >>> are so deeply intertwined. A new amd_evsel_open_strerror_check >>> sounds like it'd duplicate too much of the common function code >>> in order to handle the common error cases. >> >> Hi Kim, >> Sorry for the confusion, what I meant by adding new function is just >> to handle these corner error cases and not duplicating whole >> evsel__open_strerror code. >> >> Maybe something like below code, Its just prototype of code to show you >> the flow, you can refine it and check for any build or indentation >> issues using checkpatch.pl script. >> >> So basically, in common function we can just have 2 calls, first to >> check if we are in amd system and second to return corresponding error >> message, rather then adding whole chunk of if's which are specific to >> amd. >> >> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c >> index ac0127be0459..adefb162ae08 100644 >> --- a/tools/perf/util/evsel.c >> +++ b/tools/perf/util/evsel.c >> @@ -2852,9 +2852,40 @@ static bool find_process(const char *name) >> return ret ? false : true; >> } >> >> +static bool is_amd(const char *arch, const char *cpuid) >> +{ >> + return arch && !strcmp("x86", arch) && cpuid && strstarts(cpuid, >> "AuthenticAMD"); >> +} >> + >> +static int error_amd_ibs_brs(struct evsel *evsel, char *msg, size_t >> size) >> +{ >> + if (evsel->core.attr.precise_ip || !strncmp(evsel->pmu_name, >> "ibs", 3)) { >> + if (evsel->core.attr.exclude_kernel) >> + return scnprintf(msg, size, >> + "AMD IBS can't exclude kernel events. Try running at a higher >> privilege level."); >> + if (!evsel->core.system_wide) >> + return scnprintf(msg, size, >> + "AMD IBS may only be available in system-wide/per-cpu mode. Try >> using -a, or -C and workload affinity"); >> + } >> + >> + if (((evsel->core.attr.config & 0xff) == 0xc4) && >> (evsel->core.attr.sample_type & PERF_SAMPLE_BRANCH_STACK)) { >> + if (evsel->core.attr.freq) { >> + return scnprintf(msg, size, >> + "AMD Branch Sampling does not support frequency mode sampling, >> must pass a fixed sampling >> + period via -c option or cpu/branch-brs,period=xxxx/."); >> + /* another reason is that the period is too small */ >> + return scnprintf(msg, size, >> + "AMD Branch Sampling does not support sampling period smaller >> than what is reported in /sys/devices/cpu/caps/branches."); >> + } >> + } >> +} >> + >> int evsel__open_strerror(struct evsel *evsel, struct target *target, >> int err, char *msg, size_t size) >> { >> + struct perf_env *env = evsel__env(evsel); >> + const char *arch = perf_env__arch(env); >> + const char *cpuid = perf_env__cpuid(env); >> char sbuf[STRERR_BUFSIZE]; >> int printed = 0, enforced = 0; >> >> @@ -2950,6 +2981,8 @@ int evsel__open_strerror(struct evsel *evsel, >> struct target *target, >> return scnprintf(msg, size, "wrong clockid >> (%d).", clockid); >> if (perf_missing_features.aux_output) >> return scnprintf(msg, size, "The 'aux_output' >> feature is not supported, update the kernel."); >> + if (is_amd(arch, cpuid)) >> + return error_amd_ibs_brs(evsel, msg, size); >> break; >> case ENODATA: >> return scnprintf(msg, size, "Cannot collect data source >> with the load latency event alone. " > > That change will makes AMD machines fail to fall back to the default > "The sys_perf_event_open() syscall returned with..." error string > in case it's not those AMD IBS and BRS sub-conditions.
Yes right, as I mentioned before, the code I pointed was just a prototype to show you the flow, these corner cases can be handled on top of it.
> > Is having the AMD error code checking in the main evsel__open_strerror() > so bad? Other arches and their PMU implementations may find error > conditions that they have in common with AMD's, therefore > opening up the code for opposite types of refactoring and > reuse than what is being requested here. E.g., I've seen > other hardware configurations - not specific to one architecture - > that could also use this message: >
From my understanding, adding too many checks in common function for a specific arch is not a good practice. Since you already adding multiple functions to get information like ,if current system is amd/ibs/brs. Can't we rather just add a single function and handled all these checks there? That's just my thoughts, if maintainers are ok with it, then its fine for me too.
Thanks, Kajol Jain
> {"AMD IBS"->"%s",pmu_name} may only be available in system-wide/per-cpu > mode. Try using -a, or -C and workload affinity"); > > Thanks, > > Kim
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