The simple_ondemand devfreq governor uses two thresholds to decide about
the frequency change: upthreshold, downdifferential. These two tunable
change the behavior of the governor decision, e.g. how fast to increase
the frequency or how rapidly limit the frequency. This patch adds needed
governor data with thresholds values gathered experimentally in different
workloads.
Signed-off-by: Lukasz Luba <[email protected]>
---
Hi all,
This patch aims to improve the panfrost performance in various workloads,
(benchmarks, games). The simple_ondemand devfreq governor supports
tunables to tweak the behaviour of the internal algorithm. The default
values for these two thresholds (90 and 5) do not work well with panfrost.
These new settings should provide good performance, short latency for
rising the frequency due to rapid workload change and decent freq slow
down when the load is decaying. Based on frequency change statistics,
gathered during experiments, all frequencies are used, depending on
the load. This provides some power savings (statistically). The highest
frequency is also used when needed.
Example glmark2 results:
1. freq fixed to max: 153
2. these new thresholds values (w/ patch): 151
3. default governor values (w/o patch): 114
In future the devfreq framework would expose via sysfs these two
tunables, so they can be adjusted by the middleware based on currently
running workload (game, desktop, web browser, etc). These new values
should be good enough, though.
Regards,
Lukasz Luba
drivers/gpu/drm/panfrost/panfrost_devfreq.c | 10 +++++++++-
drivers/gpu/drm/panfrost/panfrost_devfreq.h | 2 ++
2 files changed, 11 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.c b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
index 56b3f5935703..7c5ffc81dce1 100644
--- a/drivers/gpu/drm/panfrost/panfrost_devfreq.c
+++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
@@ -130,8 +130,16 @@ int panfrost_devfreq_init(struct panfrost_device *pfdev)
panfrost_devfreq_profile.initial_freq = cur_freq;
dev_pm_opp_put(opp);
+ /*
+ * Setup default thresholds for the simple_ondemand governor.
+ * The values are chosen based on experiments.
+ */
+ pfdevfreq->gov_data.upthreshold = 45;
+ pfdevfreq->gov_data.downdifferential = 5;
+
devfreq = devm_devfreq_add_device(dev, &panfrost_devfreq_profile,
- DEVFREQ_GOV_SIMPLE_ONDEMAND, NULL);
+ DEVFREQ_GOV_SIMPLE_ONDEMAND,
+ &pfdevfreq->gov_data);
if (IS_ERR(devfreq)) {
DRM_DEV_ERROR(dev, "Couldn't initialize GPU devfreq\n");
ret = PTR_ERR(devfreq);
diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.h b/drivers/gpu/drm/panfrost/panfrost_devfreq.h
index db6ea48e21f9..1e2a4de941aa 100644
--- a/drivers/gpu/drm/panfrost/panfrost_devfreq.h
+++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.h
@@ -4,6 +4,7 @@
#ifndef __PANFROST_DEVFREQ_H__
#define __PANFROST_DEVFREQ_H__
+#include <linux/devfreq.h>
#include <linux/spinlock.h>
#include <linux/ktime.h>
@@ -17,6 +18,7 @@ struct panfrost_devfreq {
struct devfreq *devfreq;
struct opp_table *regulators_opp_table;
struct thermal_cooling_device *cooling;
+ struct devfreq_simple_ondemand_data gov_data;
bool opp_of_table_added;
ktime_t busy_time;
--
2.17.1
On 21/01/2021 18:04, Lukasz Luba wrote:
> The simple_ondemand devfreq governor uses two thresholds to decide about
> the frequency change: upthreshold, downdifferential. These two tunable
> change the behavior of the governor decision, e.g. how fast to increase
> the frequency or how rapidly limit the frequency. This patch adds needed
> governor data with thresholds values gathered experimentally in different
> workloads.
>
> Signed-off-by: Lukasz Luba <[email protected]>
> ---
> Hi all,
>
> This patch aims to improve the panfrost performance in various workloads,
> (benchmarks, games). The simple_ondemand devfreq governor supports
> tunables to tweak the behaviour of the internal algorithm. The default
> values for these two thresholds (90 and 5) do not work well with panfrost.
> These new settings should provide good performance, short latency for
> rising the frequency due to rapid workload change and decent freq slow
> down when the load is decaying. Based on frequency change statistics,
> gathered during experiments, all frequencies are used, depending on
> the load. This provides some power savings (statistically). The highest
> frequency is also used when needed.
>
> Example glmark2 results:
> 1. freq fixed to max: 153
> 2. these new thresholds values (w/ patch): 151
> 3. default governor values (w/o patch): 114
>
> In future the devfreq framework would expose via sysfs these two
> tunables, so they can be adjusted by the middleware based on currently
> running workload (game, desktop, web browser, etc). These new values
> should be good enough, though.
>
> Regards,
> Lukasz Luba
>
> drivers/gpu/drm/panfrost/panfrost_devfreq.c | 10 +++++++++-
> drivers/gpu/drm/panfrost/panfrost_devfreq.h | 2 ++
> 2 files changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.c b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> index 56b3f5935703..7c5ffc81dce1 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> @@ -130,8 +130,16 @@ int panfrost_devfreq_init(struct panfrost_device *pfdev)
> panfrost_devfreq_profile.initial_freq = cur_freq;
> dev_pm_opp_put(opp);
>
> + /*
> + * Setup default thresholds for the simple_ondemand governor.
> + * The values are chosen based on experiments.
> + */
> + pfdevfreq->gov_data.upthreshold = 45;
> + pfdevfreq->gov_data.downdifferential = 5;
> +
> devfreq = devm_devfreq_add_device(dev, &panfrost_devfreq_profile,
> - DEVFREQ_GOV_SIMPLE_ONDEMAND, NULL);
> + DEVFREQ_GOV_SIMPLE_ONDEMAND,
> + &pfdevfreq->gov_data);
> if (IS_ERR(devfreq)) {
> DRM_DEV_ERROR(dev, "Couldn't initialize GPU devfreq\n");
> ret = PTR_ERR(devfreq);
> diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.h b/drivers/gpu/drm/panfrost/panfrost_devfreq.h
> index db6ea48e21f9..1e2a4de941aa 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_devfreq.h
> +++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.h
> @@ -4,6 +4,7 @@
> #ifndef __PANFROST_DEVFREQ_H__
> #define __PANFROST_DEVFREQ_H__
>
> +#include <linux/devfreq.h>
> #include <linux/spinlock.h>
> #include <linux/ktime.h>
>
> @@ -17,6 +18,7 @@ struct panfrost_devfreq {
> struct devfreq *devfreq;
> struct opp_table *regulators_opp_table;
> struct thermal_cooling_device *cooling;
> + struct devfreq_simple_ondemand_data gov_data;
> bool opp_of_table_added;
>
> ktime_t busy_time;
I think it is simpler to do:
+static struct devfreq_simple_ondemand_data panfrost_ondemand_data = {
+ .upthreshold = 45,
+ .downdifferential = 5,
+};
[ ... ]
devfreq = devm_devfreq_add_device(dev, &panfrost_devfreq_profile,
- DEVFREQ_GOV_SIMPLE_ONDEMAND,
NULL);
+ DEVFREQ_GOV_SIMPLE_ONDEMAND,
+ &panfrost_ondemand_data);
--
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On 21/01/2021 17:04, Lukasz Luba wrote:
> The simple_ondemand devfreq governor uses two thresholds to decide about
> the frequency change: upthreshold, downdifferential. These two tunable
> change the behavior of the governor decision, e.g. how fast to increase
> the frequency or how rapidly limit the frequency. This patch adds needed
> governor data with thresholds values gathered experimentally in different
> workloads.
>
> Signed-off-by: Lukasz Luba <[email protected]>
> ---
> Hi all,
>
> This patch aims to improve the panfrost performance in various workloads,
> (benchmarks, games). The simple_ondemand devfreq governor supports
> tunables to tweak the behaviour of the internal algorithm. The default
> values for these two thresholds (90 and 5) do not work well with panfrost.
> These new settings should provide good performance, short latency for
> rising the frequency due to rapid workload change and decent freq slow
> down when the load is decaying. Based on frequency change statistics,
> gathered during experiments, all frequencies are used, depending on
> the load. This provides some power savings (statistically). The highest
> frequency is also used when needed.
>
> Example glmark2 results:
> 1. freq fixed to max: 153
> 2. these new thresholds values (w/ patch): 151
> 3. default governor values (w/o patch): 114
It would be good to state which platform this is on as this obviously
can vary depending on the OPPs available.
Of course the real fix here would be to improve the utilisation of the
GPU[1] so we actually hit the 90% threshold more easily (AFAICT kbase
uses the default 90/5 thresholds), but this seems like a reasonable
change for now.
Reviewed-by: Steven Price <[email protected]>
Thanks,
Steve
[1] When I get some time I need to rework the "queue jobs on the
hardware"[2] patch I posted ages ago. Last time it actually caused a
performance regression though...
[2] https://lore.kernel.org/r/20190816093107.30518-2-steven.price%40arm.com
> In future the devfreq framework would expose via sysfs these two
> tunables, so they can be adjusted by the middleware based on currently
> running workload (game, desktop, web browser, etc). These new values
> should be good enough, though.
>
> Regards,
> Lukasz Luba
>
> drivers/gpu/drm/panfrost/panfrost_devfreq.c | 10 +++++++++-
> drivers/gpu/drm/panfrost/panfrost_devfreq.h | 2 ++
> 2 files changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.c b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> index 56b3f5935703..7c5ffc81dce1 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> @@ -130,8 +130,16 @@ int panfrost_devfreq_init(struct panfrost_device *pfdev)
> panfrost_devfreq_profile.initial_freq = cur_freq;
> dev_pm_opp_put(opp);
>
> + /*
> + * Setup default thresholds for the simple_ondemand governor.
> + * The values are chosen based on experiments.
> + */
> + pfdevfreq->gov_data.upthreshold = 45;
> + pfdevfreq->gov_data.downdifferential = 5;
> +
> devfreq = devm_devfreq_add_device(dev, &panfrost_devfreq_profile,
> - DEVFREQ_GOV_SIMPLE_ONDEMAND, NULL);
> + DEVFREQ_GOV_SIMPLE_ONDEMAND,
> + &pfdevfreq->gov_data);
> if (IS_ERR(devfreq)) {
> DRM_DEV_ERROR(dev, "Couldn't initialize GPU devfreq\n");
> ret = PTR_ERR(devfreq);
> diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.h b/drivers/gpu/drm/panfrost/panfrost_devfreq.h
> index db6ea48e21f9..1e2a4de941aa 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_devfreq.h
> +++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.h
> @@ -4,6 +4,7 @@
> #ifndef __PANFROST_DEVFREQ_H__
> #define __PANFROST_DEVFREQ_H__
>
> +#include <linux/devfreq.h>
> #include <linux/spinlock.h>
> #include <linux/ktime.h>
>
> @@ -17,6 +18,7 @@ struct panfrost_devfreq {
> struct devfreq *devfreq;
> struct opp_table *regulators_opp_table;
> struct thermal_cooling_device *cooling;
> + struct devfreq_simple_ondemand_data gov_data;
> bool opp_of_table_added;
>
> ktime_t busy_time;
>
On 1/22/21 8:21 AM, Steven Price wrote:
> On 21/01/2021 17:04, Lukasz Luba wrote:
>> The simple_ondemand devfreq governor uses two thresholds to decide about
>> the frequency change: upthreshold, downdifferential. These two tunable
>> change the behavior of the governor decision, e.g. how fast to increase
>> the frequency or how rapidly limit the frequency. This patch adds needed
>> governor data with thresholds values gathered experimentally in different
>> workloads.
>>
>> Signed-off-by: Lukasz Luba <[email protected]>
>> ---
>> Hi all,
>>
>> This patch aims to improve the panfrost performance in various workloads,
>> (benchmarks, games). The simple_ondemand devfreq governor supports
>> tunables to tweak the behaviour of the internal algorithm. The default
>> values for these two thresholds (90 and 5) do not work well with
>> panfrost.
>> These new settings should provide good performance, short latency for
>> rising the frequency due to rapid workload change and decent freq slow
>> down when the load is decaying. Based on frequency change statistics,
>> gathered during experiments, all frequencies are used, depending on
>> the load. This provides some power savings (statistically). The highest
>> frequency is also used when needed.
>>
>> Example glmark2 results:
>> 1. freq fixed to max: 153
>> 2. these new thresholds values (w/ patch): 151
>> 3. default governor values (w/o patch): 114
>
> It would be good to state which platform this is on as this obviously
> can vary depending on the OPPs available.
Sorry about that. It was Rock Pi 4B and I have mesa 20.2.4.
>
> Of course the real fix here would be to improve the utilisation of the
> GPU[1] so we actually hit the 90% threshold more easily (AFAICT kbase
> uses the default 90/5 thresholds), but this seems like a reasonable
> change for now.
Agree, improving the scheduler would be the best option. I'll have a
look at that patch and why it got this 10% lower performance. Maybe
I would find something during testing.
>
> Reviewed-by: Steven Price <[email protected]>
Thank you for the review. I guess this patch would go through drm tree?
Regards,
Lukasz
>
> Thanks,
>
> Steve
>
> [1] When I get some time I need to rework the "queue jobs on the
> hardware"[2] patch I posted ages ago. Last time it actually caused a
> performance regression though...
>
> [2] https://lore.kernel.org/r/20190816093107.30518-2-steven.price%40arm.com
>
On 1/21/21 5:15 PM, Daniel Lezcano wrote:
> On 21/01/2021 18:04, Lukasz Luba wrote:
>> The simple_ondemand devfreq governor uses two thresholds to decide about
>> the frequency change: upthreshold, downdifferential. These two tunable
>> change the behavior of the governor decision, e.g. how fast to increase
>> the frequency or how rapidly limit the frequency. This patch adds needed
>> governor data with thresholds values gathered experimentally in different
>> workloads.
>>
>> Signed-off-by: Lukasz Luba <[email protected]>
>> ---
>> Hi all,
>>
>> This patch aims to improve the panfrost performance in various workloads,
>> (benchmarks, games). The simple_ondemand devfreq governor supports
>> tunables to tweak the behaviour of the internal algorithm. The default
>> values for these two thresholds (90 and 5) do not work well with panfrost.
>> These new settings should provide good performance, short latency for
>> rising the frequency due to rapid workload change and decent freq slow
>> down when the load is decaying. Based on frequency change statistics,
>> gathered during experiments, all frequencies are used, depending on
>> the load. This provides some power savings (statistically). The highest
>> frequency is also used when needed.
>>
>> Example glmark2 results:
>> 1. freq fixed to max: 153
>> 2. these new thresholds values (w/ patch): 151
>> 3. default governor values (w/o patch): 114
>>
>> In future the devfreq framework would expose via sysfs these two
>> tunables, so they can be adjusted by the middleware based on currently
>> running workload (game, desktop, web browser, etc). These new values
>> should be good enough, though.
>>
>> Regards,
>> Lukasz Luba
>>
>> drivers/gpu/drm/panfrost/panfrost_devfreq.c | 10 +++++++++-
>> drivers/gpu/drm/panfrost/panfrost_devfreq.h | 2 ++
>> 2 files changed, 11 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.c b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
>> index 56b3f5935703..7c5ffc81dce1 100644
>> --- a/drivers/gpu/drm/panfrost/panfrost_devfreq.c
>> +++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
>> @@ -130,8 +130,16 @@ int panfrost_devfreq_init(struct panfrost_device *pfdev)
>> panfrost_devfreq_profile.initial_freq = cur_freq;
>> dev_pm_opp_put(opp);
>>
>> + /*
>> + * Setup default thresholds for the simple_ondemand governor.
>> + * The values are chosen based on experiments.
>> + */
>> + pfdevfreq->gov_data.upthreshold = 45;
>> + pfdevfreq->gov_data.downdifferential = 5;
>> +
>> devfreq = devm_devfreq_add_device(dev, &panfrost_devfreq_profile,
>> - DEVFREQ_GOV_SIMPLE_ONDEMAND, NULL);
>> + DEVFREQ_GOV_SIMPLE_ONDEMAND,
>> + &pfdevfreq->gov_data);
>> if (IS_ERR(devfreq)) {
>> DRM_DEV_ERROR(dev, "Couldn't initialize GPU devfreq\n");
>> ret = PTR_ERR(devfreq);
>> diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.h b/drivers/gpu/drm/panfrost/panfrost_devfreq.h
>> index db6ea48e21f9..1e2a4de941aa 100644
>> --- a/drivers/gpu/drm/panfrost/panfrost_devfreq.h
>> +++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.h
>> @@ -4,6 +4,7 @@
>> #ifndef __PANFROST_DEVFREQ_H__
>> #define __PANFROST_DEVFREQ_H__
>>
>> +#include <linux/devfreq.h>
>> #include <linux/spinlock.h>
>> #include <linux/ktime.h>
>>
>> @@ -17,6 +18,7 @@ struct panfrost_devfreq {
>> struct devfreq *devfreq;
>> struct opp_table *regulators_opp_table;
>> struct thermal_cooling_device *cooling;
>> + struct devfreq_simple_ondemand_data gov_data;
>> bool opp_of_table_added;
>>
>> ktime_t busy_time;
>
> I think it is simpler to do:
>
> +static struct devfreq_simple_ondemand_data panfrost_ondemand_data = {
> + .upthreshold = 45,
> + .downdifferential = 5,
> +};
>
> [ ... ]
>
> devfreq = devm_devfreq_add_device(dev, &panfrost_devfreq_profile,
> - DEVFREQ_GOV_SIMPLE_ONDEMAND,
> NULL);
> + DEVFREQ_GOV_SIMPLE_ONDEMAND,
> + &panfrost_ondemand_data);
>
>
Yes, it's simpler. The driver would probably never have to serve two
GPUs. I've tried to keep this thing inside the panfrost struct,
forgetting about it.
Steven already reviewed the patch, so it can probably stay.
I will keep it in mind. Thank you for the comments.
Regards,
Lukasz
On 22/01/2021 10:11, Lukasz Luba wrote:
>
>
> On 1/21/21 5:15 PM, Daniel Lezcano wrote:
>> On 21/01/2021 18:04, Lukasz Luba wrote:
>>> The simple_ondemand devfreq governor uses two thresholds to decide about
>>> the frequency change: upthreshold, downdifferential. These two tunable
>>> change the behavior of the governor decision, e.g. how fast to increase
>>> the frequency or how rapidly limit the frequency. This patch adds needed
>>> governor data with thresholds values gathered experimentally in
>>> different
>>> workloads.
>>>
>>> Signed-off-by: Lukasz Luba <[email protected]>
>>> ---
>>> Hi all,
>>>
>>> This patch aims to improve the panfrost performance in various
>>> workloads,
>>> (benchmarks, games). The simple_ondemand devfreq governor supports
>>> tunables to tweak the behaviour of the internal algorithm. The default
>>> values for these two thresholds (90 and 5) do not work well with
>>> panfrost.
>>> These new settings should provide good performance, short latency for
>>> rising the frequency due to rapid workload change and decent freq slow
>>> down when the load is decaying. Based on frequency change statistics,
>>> gathered during experiments, all frequencies are used, depending on
>>> the load. This provides some power savings (statistically). The highest
>>> frequency is also used when needed.
>>>
>>> Example glmark2 results:
>>> 1. freq fixed to max: 153
>>> 2. these new thresholds values (w/ patch): 151
>>> 3. default governor values (w/o patch): 114
>>>
>>> In future the devfreq framework would expose via sysfs these two
>>> tunables, so they can be adjusted by the middleware based on currently
>>> running workload (game, desktop, web browser, etc). These new values
>>> should be good enough, though.
>>>
>>> Regards,
>>> Lukasz Luba
>>>
>>> drivers/gpu/drm/panfrost/panfrost_devfreq.c | 10 +++++++++-
>>> drivers/gpu/drm/panfrost/panfrost_devfreq.h | 2 ++
>>> 2 files changed, 11 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.c
>>> b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
>>> index 56b3f5935703..7c5ffc81dce1 100644
>>> --- a/drivers/gpu/drm/panfrost/panfrost_devfreq.c
>>> +++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
>>> @@ -130,8 +130,16 @@ int panfrost_devfreq_init(struct panfrost_device
>>> *pfdev)
>>> panfrost_devfreq_profile.initial_freq = cur_freq;
>>> dev_pm_opp_put(opp);
>>> + /*
>>> + * Setup default thresholds for the simple_ondemand governor.
>>> + * The values are chosen based on experiments.
>>> + */
>>> + pfdevfreq->gov_data.upthreshold = 45;
>>> + pfdevfreq->gov_data.downdifferential = 5;
>>> +
>>> devfreq = devm_devfreq_add_device(dev, &panfrost_devfreq_profile,
>>> - DEVFREQ_GOV_SIMPLE_ONDEMAND, NULL);
>>> + DEVFREQ_GOV_SIMPLE_ONDEMAND,
>>> + &pfdevfreq->gov_data);
>>> if (IS_ERR(devfreq)) {
>>> DRM_DEV_ERROR(dev, "Couldn't initialize GPU devfreq\n");
>>> ret = PTR_ERR(devfreq);
>>> diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.h
>>> b/drivers/gpu/drm/panfrost/panfrost_devfreq.h
>>> index db6ea48e21f9..1e2a4de941aa 100644
>>> --- a/drivers/gpu/drm/panfrost/panfrost_devfreq.h
>>> +++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.h
>>> @@ -4,6 +4,7 @@
>>> #ifndef __PANFROST_DEVFREQ_H__
>>> #define __PANFROST_DEVFREQ_H__
>>> +#include <linux/devfreq.h>
>>> #include <linux/spinlock.h>
>>> #include <linux/ktime.h>
>>> @@ -17,6 +18,7 @@ struct panfrost_devfreq {
>>> struct devfreq *devfreq;
>>> struct opp_table *regulators_opp_table;
>>> struct thermal_cooling_device *cooling;
>>> + struct devfreq_simple_ondemand_data gov_data;
>>> bool opp_of_table_added;
>>> ktime_t busy_time;
>>
>> I think it is simpler to do:
>>
>> +static struct devfreq_simple_ondemand_data panfrost_ondemand_data = {
>> + .upthreshold = 45,
>> + .downdifferential = 5,
>> +};
>>
>> [ ... ]
>>
>> devfreq = devm_devfreq_add_device(dev, &panfrost_devfreq_profile,
>> - DEVFREQ_GOV_SIMPLE_ONDEMAND,
>> NULL);
>> + DEVFREQ_GOV_SIMPLE_ONDEMAND,
>> + &panfrost_ondemand_data);
>>
>>
>
> Yes, it's simpler. The driver would probably never have to serve two
> GPUs. I've tried to keep this thing inside the panfrost struct,
> forgetting about it.
The Juno platform with an FPGA attached is the only example I know of
where a system has multiple Mali GPUs - so it can happen, but it rare.
As it stands a static structure would work because the values are
constant - but Lukasz mentioned that they would be exported in sysfs in
the future, in which case they really should be part of the panfrost struct.
Ultimately having a (non-const) static struct like above would mean
wasting a few bytes on systems with Panfrost loaded but no Mali GPU.
Having it in struct panfrost means the cost is only for Mali. Admittedly
it's only a few bytes in this case and often Panfrost will be a module.
Steve
> Steven already reviewed the patch, so it can probably stay.
> I will keep it in mind. Thank you for the comments.
>
> Regards,
> Lukasz
On 22/01/2021 10:00, Lukasz Luba wrote:
>
>
> On 1/22/21 8:21 AM, Steven Price wrote:
>> On 21/01/2021 17:04, Lukasz Luba wrote:
>>> The simple_ondemand devfreq governor uses two thresholds to decide about
>>> the frequency change: upthreshold, downdifferential. These two tunable
>>> change the behavior of the governor decision, e.g. how fast to increase
>>> the frequency or how rapidly limit the frequency. This patch adds needed
>>> governor data with thresholds values gathered experimentally in
>>> different
>>> workloads.
>>>
>>> Signed-off-by: Lukasz Luba <[email protected]>
>>> ---
>>> Hi all,
>>>
>>> This patch aims to improve the panfrost performance in various
>>> workloads,
>>> (benchmarks, games). The simple_ondemand devfreq governor supports
>>> tunables to tweak the behaviour of the internal algorithm. The default
>>> values for these two thresholds (90 and 5) do not work well with
>>> panfrost.
>>> These new settings should provide good performance, short latency for
>>> rising the frequency due to rapid workload change and decent freq slow
>>> down when the load is decaying. Based on frequency change statistics,
>>> gathered during experiments, all frequencies are used, depending on
>>> the load. This provides some power savings (statistically). The highest
>>> frequency is also used when needed.
>>>
>>> Example glmark2 results:
>>> 1. freq fixed to max: 153
>>> 2. these new thresholds values (w/ patch): 151
>>> 3. default governor values (w/o patch): 114
>>
>> It would be good to state which platform this is on as this obviously
>> can vary depending on the OPPs available.
>
> Sorry about that. It was Rock Pi 4B and I have mesa 20.2.4.
>
>>
>> Of course the real fix here would be to improve the utilisation of the
>> GPU[1] so we actually hit the 90% threshold more easily (AFAICT kbase
>> uses the default 90/5 thresholds), but this seems like a reasonable
>> change for now.
>
> Agree, improving the scheduler would be the best option. I'll have a
> look at that patch and why it got this 10% lower performance. Maybe
> I would find something during testing.
I'm afraid it'll probably need a fair bit of work to rebase - things
have changed around that code. I'm hoping that most of the problem was
really around how Mesa was driving the GPU at that time and things
should be better. The DDK (hacked to talk Panfrost ioctls) saw a
performance improvement.
Let me know if you hit problems and need any help.
>>
>> Reviewed-by: Steven Price <[email protected]>
>
> Thank you for the review. I guess this patch would go through drm tree?
Yes, I'll push it to drm-misc-next later.
Thanks,
Steve
> Regards,
> Lukasz
>
>>
>> Thanks,
>>
>> Steve
>>
>> [1] When I get some time I need to rework the "queue jobs on the
>> hardware"[2] patch I posted ages ago. Last time it actually caused a
>> performance regression though...
>>
>> [2]
>> https://lore.kernel.org/r/20190816093107.30518-2-steven.price%40arm.com
>>
On 1/22/21 10:24 AM, Steven Price wrote:
> On 22/01/2021 10:00, Lukasz Luba wrote:
>>
>>
>> On 1/22/21 8:21 AM, Steven Price wrote:
>>> On 21/01/2021 17:04, Lukasz Luba wrote:
>>>> The simple_ondemand devfreq governor uses two thresholds to decide
>>>> about
>>>> the frequency change: upthreshold, downdifferential. These two tunable
>>>> change the behavior of the governor decision, e.g. how fast to increase
>>>> the frequency or how rapidly limit the frequency. This patch adds
>>>> needed
>>>> governor data with thresholds values gathered experimentally in
>>>> different
>>>> workloads.
>>>>
>>>> Signed-off-by: Lukasz Luba <[email protected]>
>>>> ---
>>>> Hi all,
>>>>
>>>> This patch aims to improve the panfrost performance in various
>>>> workloads,
>>>> (benchmarks, games). The simple_ondemand devfreq governor supports
>>>> tunables to tweak the behaviour of the internal algorithm. The default
>>>> values for these two thresholds (90 and 5) do not work well with
>>>> panfrost.
>>>> These new settings should provide good performance, short latency for
>>>> rising the frequency due to rapid workload change and decent freq slow
>>>> down when the load is decaying. Based on frequency change statistics,
>>>> gathered during experiments, all frequencies are used, depending on
>>>> the load. This provides some power savings (statistically). The highest
>>>> frequency is also used when needed.
>>>>
>>>> Example glmark2 results:
>>>> 1. freq fixed to max: 153
>>>> 2. these new thresholds values (w/ patch): 151
>>>> 3. default governor values (w/o patch): 114
>>>
>>> It would be good to state which platform this is on as this obviously
>>> can vary depending on the OPPs available.
>>
>> Sorry about that. It was Rock Pi 4B and I have mesa 20.2.4.
>>
>>>
>>> Of course the real fix here would be to improve the utilisation of
>>> the GPU[1] so we actually hit the 90% threshold more easily (AFAICT
>>> kbase uses the default 90/5 thresholds), but this seems like a
>>> reasonable change for now.
>>
>> Agree, improving the scheduler would be the best option. I'll have a
>> look at that patch and why it got this 10% lower performance. Maybe
>> I would find something during testing.
>
> I'm afraid it'll probably need a fair bit of work to rebase - things
> have changed around that code. I'm hoping that most of the problem was
> really around how Mesa was driving the GPU at that time and things
> should be better. The DDK (hacked to talk Panfrost ioctls) saw a
> performance improvement.
>
> Let me know if you hit problems and need any help.
OK, I will contact you when I face some problems.
>
>>>
>>> Reviewed-by: Steven Price <[email protected]>
>>
>> Thank you for the review. I guess this patch would go through drm tree?
>
> Yes, I'll push it to drm-misc-next later.
Thank you!
Lukasz