Messages in this thread Patch in this message | | | From | Valentin Schneider <> | Subject | Re: [PATCH v3] sched/topology: remove sysctl_sched_energy_aware depending on the architecture | Date | Fri, 15 Sep 2023 14:00:15 +0200 |
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On 14/09/23 23:26, Shrikanth Hegde wrote: > On 9/14/23 9:51 PM, Valentin Schneider wrote: >> On 13/09/23 17:18, Shrikanth Hegde wrote: >>> sysctl_sched_energy_aware is available for the admin to disable/enable >>> energy aware scheduling(EAS). EAS is enabled only if few conditions are >>> met by the platform. They are, asymmetric CPU capacity, no SMT, >>> valid cpufreq policy, frequency invariant load tracking. It is possible >>> platform when booting may not have EAS capability, but can do that after. >>> For example, changing/registering the cpufreq policy. >>> >>> At present, though platform doesn't support EAS, this sysctl is still >>> present and it ends up calling rebuild of sched domain on write to 1 and >>> NOP when writing to 0. That is confusing and un-necessary. >>> >> > > Hi Valentin, Thanks for taking a look at this patch. > >> But why would you write to it in the first place? Or do you mean to use >> this as an indicator for userspace that EAS is supported? >> > > Since this sysctl is present and its value being 1, it gives the > impression to the user that EAS is supported when it is not. > So its an attempt to correct that part. >
Ah, I see. Then how about just making the sysctl return 0 when EAS isn't supported? And on top of it, prevent all writes when EAS isn't supported (perf domains cannot be built, so there would be no point in forcing a rebuild that will do nothing).
I can never remember how to properly use the sysctl API, so that's a very crude implementation, but something like so?
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diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index 05a5bc678c089..dadfc5afc4121 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -230,9 +230,28 @@ static int sched_energy_aware_handler(struct ctl_table *table, int write, if (write && !capable(CAP_SYS_ADMIN)) return -EPERM; + if (!sched_energy_enabled()) { + if (write) + return -EOPNOTSUPP; + else { + size_t len; + + if (*ppos) { + *lenp = 0; + return 0; + } + + len = snprintf((char *)buffer, 3, "0\n"); + + *lenp = len; + *ppos += len; + return 0; + } + } + ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); if (!ret && write) { - state = static_branch_unlikely(&sched_energy_present); + state = sched_energy_enabled(); if (state != sysctl_sched_energy_aware) rebuild_sched_domains_energy(); }
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