Hi Michal, On 15-Jul 18:42, Michal Koutný wrote: > On Mon, Jul 08, 2019 at 09:43:54AM +0100, Patrick Bellasi > <patrick.bell...@arm.com> wrote: > > Since it's possible for a cpu.uclamp.min value to be bigger than the > > cpu.uclamp.max value, ensure local consistency by restricting each > > "protection" > > (i.e. min utilization) with the corresponding "limit" (i.e. max > > utilization). > I think this constraint should be mentioned in the Documentation/....
That note comes from the previous review cycle and it's based on a request from Tejun to align uclamp behaviors with the way the delegation model is supposed to work. I guess this part of the documentation: https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html?highlight=protections#resource-distribution-models should already cover the expected uclamp min/max behaviors. However, I guess "repetita iuvant" in this case. I'll call this out explicitly in the description of cpu.uclamp.min. > > +static void cpu_util_update_eff(struct cgroup_subsys_state *css) > > +{ > > + struct cgroup_subsys_state *top_css = css; > > + struct uclamp_se *uc_se = NULL; > > + unsigned int eff[UCLAMP_CNT]; > > + unsigned int clamp_id; > > + unsigned int clamps; > > + > > + css_for_each_descendant_pre(css, top_css) { > > + uc_se = css_tg(css)->parent > > + ? css_tg(css)->parent->uclamp : NULL; > > + > > + for_each_clamp_id(clamp_id) { > > + /* Assume effective clamps matches requested clamps */ > > + eff[clamp_id] = css_tg(css)->uclamp_req[clamp_id].value; > > + /* Cap effective clamps with parent's effective clamps > > */ > > + if (uc_se && > > + eff[clamp_id] > uc_se[clamp_id].value) { > > + eff[clamp_id] = uc_se[clamp_id].value; > > + } > > + } > > + /* Ensure protection is always capped by limit */ > > + eff[UCLAMP_MIN] = min(eff[UCLAMP_MIN], eff[UCLAMP_MAX]); > > + > > + /* Propagate most restrictive effective clamps */ > > + clamps = 0x0; > > + uc_se = css_tg(css)->uclamp; > (Nitpick only, reassigning child where was parent before decreases > readibility. IMO) Did not checked but I think the compiler will figure out it can still use a single pointer for both assignments. I'll let's the compiler to its job and add in a dedicated stack var for the parent pointer. > > + for_each_clamp_id(clamp_id) { > > + if (eff[clamp_id] == uc_se[clamp_id].value) > > + continue; > > + uc_se[clamp_id].value = eff[clamp_id]; > > + uc_se[clamp_id].bucket_id = > > uclamp_bucket_id(eff[clamp_id]); > Shouldn't these writes be synchronized with writes from > __setscheduler_uclamp()? You right, the synchronization is introduced by a later patch: sched/core: uclamp: Update CPU's refcount on TG's clamp changes Cheers, Patrick -- #include <best/regards.h> Patrick Bellasi
