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X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Oct 2025 10:20:52.6588 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: f553d2fd-ff0a-4bc7-bc8c-08de04c20767 X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[4.158.2.129];Helo=[outbound-uk1.az.dlp.m.darktrace.com] X-MS-Exchange-CrossTenant-AuthSource: AM4PEPF00025F95.EURPRD83.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PAWPR08MB11437 On 9/30/25 11:04, Peter Zijlstra wrote: > On Tue, Sep 30, 2025 at 08:20:06AM +0100, Juri Lelli wrote: > >> I actually wonder if we shouldn't make cppc_fie a "special" DEADLINE >> tasks (like schedutil [1]). IIUC that is how it is thought to behave >> already [2], but, since it's missing the SCHED_FLAG_SUGOV flag(/hack), >> it is not "transparent" from a bandwidth tracking point of view. >> >> 1 - https://elixir.bootlin.com/linux/v6.17/source/kernel/sched/cpufreq_schedutil.c#L661 >> 2 - https://elixir.bootlin.com/linux/v6.17/source/drivers/cpufreq/cppc_cpufreq.c#L198 > Right, I remember that hack. Bit sad its spreading, but this CPPC thing > is very much like the schedutil one, so might as well do that I suppose. > IIUC, the sugov thread was switched to deadline to allow frequency updates when deadline tasks start to run. I.e. there should be no point updating the freq. after the deadline task finished running, cf [1] and [2] The CPPC FIE worker should not require to run that quickly as it seems to be more like a freq. maintenance work (the call comes from the sched tick) sched_tick() \-arch_scale_freq_tick() / topology_scale_freq_tick()   \-set_freq_scale() / cppc_scale_freq_tick()     \-irq_work_queue() [1] https://lore.kernel.org/all/20171204102325.5110-3-juri.lelli@redhat.com/ [2] https://lore.kernel.org/all/20171204102325.5110-1-juri.lelli@redhat.com/ """  o 03/08      it's a temporary solution to make possible (on ARM) to change               frequency for DEADLINE tasks (that would possibly delay the SCHED_FIFO               worker kthread); proper solution would be to be able to issue frequency               transition from an atomic ctx """