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Message-ID: <a41853fdaee888761ac2a34708118991b70cb904.camel@linux.intel.com>
Date: Wed, 12 Jan 2022 15:54:00 -0800
From: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
To: "Rafael J. Wysocki" <rafael@...nel.org>,
Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
Daniel Lezcano <daniel.lezcano@...aro.org>,
Linux PM <linux-pm@...r.kernel.org>,
the arch/x86 maintainers <x86@...nel.org>,
"open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
Len Brown <len.brown@...el.com>,
Aubrey Li <aubrey.li@...ux.intel.com>,
Amit Kucheria <amitk@...nel.org>,
Andi Kleen <ak@...ux.intel.com>,
Tim Chen <tim.c.chen@...ux.intel.com>,
Lukasz Luba <lukasz.luba@....com>,
"Ravi V. Shankar" <ravi.v.shankar@...el.com>,
Ricardo Neri <ricardo.neri@...el.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 7/7] thermal: intel: hfi: Notify user space for HFI
events
On Wed, 2022-01-12 at 20:53 +0100, Rafael J. Wysocki wrote:
> On Sat, Jan 8, 2022 at 4:46 AM Ricardo Neri
> <ricardo.neri-calderon@...ux.intel.com> wrote:
> > From: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
> >
> > When the hardware issues an HFI event, relay a notification to user
> > space.
> > This allows user space to respond by reading performance and
> > efficiency of
> > each CPU and take appropriate action.
> >
> > For example, when performance and efficiency of a CPU is 0, user
> > space can
> > either offline the CPU or inject idle. Also, if user space notices
> > a
> > downward trend in performance, it may proactively adjust power
> > limits to
> > avoid future situations in which performance drops to 0.
> >
> > To avoid excessive notifications, the rate is limited by one HZ per
> > event.
> > To limit the netlink message size, parameters for only 16 CPUs at
> > max are
> > sent in one message. If there are more than 16 CPUs, issue as many
> > messages
> > as needed to notify the status of all CPUs.
> >
> > In the HFI specification, both performance and efficiency
> > capabilities are
> > set in the [0, 255] range. The existing implementations of HFI
> > hardware
> > do not scale the maximum values to 255. Since userspace cares about
> > capability values that are either 0 or show a downward/upward
> > trend, this
> > fact does not matter much. Relative changes in capabilities are
> > enough. To
> > comply with the thermal netlink ABI, scale both performance and
> > efficiency
> > capabilities to the [0, 1023] interval.
> >
> > Cc: Andi Kleen <ak@...ux.intel.com>
> > Cc: Aubrey Li <aubrey.li@...ux.intel.com>
> > Cc: Lukasz Luba <lukasz.luba@....com>
> > Cc: Tim Chen <tim.c.chen@...ux.intel.com>
> > Cc: "Ravi V. Shankar" <ravi.v.shankar@...el.com>
> > Reviewed-by: Len Brown <len.brown@...el.com>
> > Signed-off-by: Srinivas Pandruvada <
> > srinivas.pandruvada@...ux.intel.com>
> > ---
> > Changes since v3:
> > * None
> >
> > Changes since v2:
> > * None
> >
> > Changes since v1:
> > * Made get_one_hfi_cap() return void. Removed unnecessary checks.
> > (Rafael)
> > * Replaced raw_spin_[un]lock_irq[restore|save]() with raw_spin_
> > [un]lock_irq() in get_one_hfi_cap(). This function is only
> > called from
> > a workqueue and there is no need to save and restore irq flags.
> > * Scaled performance and energy efficiency values to a [0, 1023]
> > interval
> > when reporting values to user space via thermal netlink
> > notifications.
> > (Lucasz).
> > * Reworded commit message to comment on the scaling of HFI
> > capabilities
> > to comply with the proposed thermal netlink ABI.
> > ---
> > drivers/thermal/intel/Kconfig | 1 +
> > drivers/thermal/intel/intel_hfi.c | 57
> > ++++++++++++++++++++++++++++++-
> > 2 files changed, 57 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/thermal/intel/Kconfig
> > b/drivers/thermal/intel/Kconfig
> > index e9d2925227d4..6cf3fe36a4ae 100644
> > --- a/drivers/thermal/intel/Kconfig
> > +++ b/drivers/thermal/intel/Kconfig
> > @@ -104,6 +104,7 @@ config INTEL_HFI_THERMAL
> > bool "Intel Hardware Feedback Interface"
> > depends on CPU_SUP_INTEL
> > depends on X86_THERMAL_VECTOR
> > + select THERMAL_NETLINK
> > help
> > Select this option to enable the Hardware Feedback
> > Interface. If
> > selected, hardware provides guidance to the operating
> > system on
> > diff --git a/drivers/thermal/intel/intel_hfi.c
> > b/drivers/thermal/intel/intel_hfi.c
> > index 1a08c58f26f6..9fd66f176948 100644
> > --- a/drivers/thermal/intel/intel_hfi.c
> > +++ b/drivers/thermal/intel/intel_hfi.c
> > @@ -40,6 +40,7 @@
> >
> > #include <asm/msr.h>
> >
> > +#include "../thermal_core.h"
> > #include "intel_hfi.h"
> >
> > #define THERM_STATUS_CLEAR_PKG_MASK (BIT(1) | BIT(3) | BIT(5) |
> > BIT(7) | \
> > @@ -162,6 +163,60 @@ static struct hfi_features hfi_features;
> > static DEFINE_MUTEX(hfi_instance_lock);
> >
> > #define HFI_UPDATE_INTERVAL HZ
> > +#define HFI_MAX_THERM_NOTIFY_COUNT 16
> > +
> > +static void get_one_hfi_cap(struct hfi_instance *hfi_instance, s16
> > index,
> > + struct hfi_cpu_data *hfi_caps)
> > +{
> > + struct hfi_cpu_data *caps;
> > +
> > + /* Find the capabilities of @cpu */
> > + raw_spin_lock_irq(&hfi_instance->table_lock);
> > + caps = hfi_instance->data + index *
> > hfi_features.cpu_stride;
> > + memcpy(hfi_caps, caps, sizeof(*hfi_caps));
> > + raw_spin_unlock_irq(&hfi_instance->table_lock);
> > +}
> > +
> > +/*
> > + * Call update_capabilities() when there are changes in the HFI
> > table.
> > + */
> > +static void update_capabilities(struct hfi_instance *hfi_instance)
> > +{
> > + struct cpu_capability cpu_caps[HFI_MAX_THERM_NOTIFY_COUNT];
> > + int i = 0, cpu;
> > +
>
> Wouldn't it be better to hold hfi_instance_lock for the duration of
> this loop?
As you expressed concern with more CPUs per package in future + netlink
processing the interrupts will be disabled for longer time.
But this can be optimized to have
void get_one_hfi_cap(struct hfi_instance *hfi_instance, s16 index,
struct hfi_cpu_data *hfi_caps)
with something like
void get_hfi_caps(struct hfi_instance *hfi_instance, s16 *cpu_count,
struct hfi_cpu_data **hfi_caps)
and take one lock for all
HFI_MAX_THERM_NOTIFY_COUNT CPUs.
Then keep thermal_genl_cpu_capability_event outside.
This ends up in calling thermal_genl_send_event() which has a long call
chain to netlink_broadcast() to format and broadcast message.
Thanks,
Srinivas
>
> Surely, CPU offline or online during it can be confusing.
>
> > + for_each_cpu(cpu, hfi_instance->cpus) {
> > + struct hfi_cpu_data caps;
> > + s16 index;
> > +
> > + /*
> > + * We know index is valid because this CPU is
> > present
> > + * in this instance.
> > + */
> > + index = per_cpu(hfi_cpu_info, cpu).index;
> > +
> > + get_one_hfi_cap(hfi_instance, index, &caps);
> > +
> > + cpu_caps[i].cpu = cpu;
> > +
> > + /*
> > + * Scale performance and energy efficiency to
> > + * the [0, 1023] interval that thermal netlink
> > uses.
> > + */
> > + cpu_caps[i].performance = caps.perf_cap << 2;
> > + cpu_caps[i].efficiency = caps.ee_cap << 2;
> > + ++i;
> > +
> > + if (i >= HFI_MAX_THERM_NOTIFY_COUNT) {
> > + thermal_genl_cpu_capability_event(HFI_MAX_T
> > HERM_NOTIFY_COUNT,
> > + cpu_caps)
> > ;
> > + i = 0;
> > + }
> > + }
> > +
> > + if (i)
> > + thermal_genl_cpu_capability_event(i, cpu_caps);
> > +}
> >
> > static void hfi_update_work_fn(struct work_struct *work)
> > {
> > @@ -172,7 +227,7 @@ static void hfi_update_work_fn(struct
> > work_struct *work)
> > if (!hfi_instance)
> > return;
> >
> > - /* TODO: Consume update here. */
> > + update_capabilities(hfi_instance);
> > }
> >
> > void intel_hfi_process_event(__u64 pkg_therm_status_msr_val)
> > --
> > 2.17.1
> >
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