Messages in this thread | | | Date | Fri, 12 Apr 2024 17:12:08 +0100 | From | Dave Martin <> | Subject | Re: [PATCH v1 05/31] x86/resctrl: Remove rdtgroup from update_cpu_closid_rmid() |
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On Mon, Apr 08, 2024 at 08:16:08PM -0700, Reinette Chatre wrote: > Hi James, > > On 3/21/2024 9:50 AM, James Morse wrote: > > update_cpu_closid_rmid() takes a struct rdtgroup as an argument, which > > it uses to update the local CPUs default pqr values. This is a problem > > once the resctrl parts move out to /fs/, as the arch code cannot > > poke around inside struct rdtgroup. > > > > Rename update_cpu_closid_rmid() as resctrl_arch_sync_cpus_defaults() > > to be used as the target of an IPI, and pass the effective CLOSID > > and RMID in a new struct. > > > > Signed-off-by: James Morse <james.morse@arm.com> > > --- > > arch/x86/kernel/cpu/resctrl/rdtgroup.c | 19 +++++++++++++++---- > > include/linux/resctrl.h | 11 +++++++++++ > > 2 files changed, 26 insertions(+), 4 deletions(-) > > > > diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c > > index 5d2c1ce5b6b1..18f097fce51e 100644 > > --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c > > +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c > > @@ -341,13 +341,13 @@ static int rdtgroup_cpus_show(struct kernfs_open_file *of, > > * from update_closid_rmid() is protected against __switch_to() because > > * preemption is disabled. > > */ > > -static void update_cpu_closid_rmid(void *info) > > +void resctrl_arch_sync_cpu_defaults(void *info) > > { > > - struct rdtgroup *r = info; > > + struct resctrl_cpu_sync *r = info; > > > > if (r) { > > this_cpu_write(pqr_state.default_closid, r->closid); > > - this_cpu_write(pqr_state.default_rmid, r->mon.rmid); > > + this_cpu_write(pqr_state.default_rmid, r->rmid); > > } > > > > /* > > @@ -362,11 +362,22 @@ static void update_cpu_closid_rmid(void *info) > > * Update the PGR_ASSOC MSR on all cpus in @cpu_mask, > > * > > * Per task closids/rmids must have been set up before calling this function. > > + * @r may be NULL. > > */ > > static void > > update_closid_rmid(const struct cpumask *cpu_mask, struct rdtgroup *r) > > { > > - on_each_cpu_mask(cpu_mask, update_cpu_closid_rmid, r, 1); > > + struct resctrl_cpu_sync defaults; > > + struct resctrl_cpu_sync *defaults_p = NULL; > > Please maintain reverse fir order.
Or, more tersely as follows?
struct resctrl_cpu_sync defaults, *defaults_p = NULL;
"Reverse fir order" seems to be documented as a preference rather than a rule.
The declarations can be swapped, but defaults_p is in some sense a weak pointer to defaults, so it feels a bit strange to declare them backwards.
Alternatively, could we rename defaults_p to p? Given the size of this function I don't think that impacts clarity.
I'll wait for your opinion on this.
> > + > > + if (r) { > > + defaults.closid = r->closid; > > + defaults.rmid = r->mon.rmid; > > + defaults_p = &defaults; > > + } > > + > > + on_each_cpu_mask(cpu_mask, resctrl_arch_sync_cpu_defaults, defaults_p, > > + 1); > > } > > > > static int cpus_mon_write(struct rdtgroup *rdtgrp, cpumask_var_t newmask, > > diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h > > index 6e87bc95f5ea..2b79e4159507 100644 > > --- a/include/linux/resctrl.h > > +++ b/include/linux/resctrl.h > > @@ -220,6 +220,17 @@ struct resctrl_schema { > > u32 num_closid; > > }; > > > > +struct resctrl_cpu_sync { > > + u32 closid; > > + u32 rmid; > > +}; > > + > > +/* > > + * Update and re-load this CPUs defaults. Called via IPI, takes a pointer to > > "this CPU's defaults"?
Ack (also in the commit message).
> > > + * struct resctrl_cpu_sync, or NULL. > > + */ > > Updating the CPU's defaults is not the primary goal of this function and because > of that I do not think this should be the focus with the main goal (updating > RMID and CLOSID on CPU) ignored. Specifically, this function only updates > the defaults if *info is set but it _always_ ensures CPU is running with > appropriate CLOSID/RMID (which may or may not be from a CPU default). > > I think resctrl_arch_sync_cpu_closid_rmid() may be more appropriate > and the comment needs to elaborate what the function does. > > > +void resctrl_arch_sync_cpu_defaults(void *info);
That seems reasonable, and follows the original naming and what the code does:
What about:
/** * resctrl_arch_sync_cpu_defaults() - Refresh the CPU's CLOSID and RMID. * Call via IPI. * @info: If non-NULL, a pointer to a struct resctrl_cpu_sync specifying * the new CLOSID and RMID for tasks in the default resctrl ctrl * and mon group when running on this CPU. If NULL, the default * CLOSID and RMID are not changed. * * This is how reassignment of CPUs and/or tasks to different resctrl groups * is propagated when requested by the resctrl fs core code. * * This function should typically record the per-cpu defaults specified by * @info (if any), and then reconfigure the CPU's hardware CLOSID and RMID * for subsequent execution based on @current, in the same way as during a * task switch. */
..?
Cheers ---Dave
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