From: Lukasz Luba <lukasz.luba@arm.com>
To: gao.yunxiao6@gmail.com, daniel.lezcano@linaro.org
Cc: rui.zhang@intel.com, amitk@kernel.org, linux-pm@vger.kernel.org,
linux-kernel@vger.kernel.org, orsonzhai@gmail.com,
zhang.lyra@gmail.com, "jeson.gao" <jeson.gao@unisoc.com>
Subject: Re: [PATCH] thermal: power_allocator: using round the division when re-divvying up power
Date: Mon, 15 Mar 2021 09:51:14 +0000 [thread overview]
Message-ID: <9c14451e-be6f-0713-4c26-8b67e1fa51a5@arm.com> (raw)
In-Reply-To: <1615796737-4688-1-git-send-email-gao.yunxiao6@gmail.com>
On 3/15/21 8:25 AM, gao.yunxiao6@gmail.com wrote:
> From: "jeson.gao" <jeson.gao@unisoc.com>
>
> The division is used directly in re-divvying up power, the decimal part will
> be discarded, devices will get less than the extra_actor_power - 1.
> if using round the division to make the calculation more accurate.
>
> For example:
> actor0 received more than it's max_power, it has the extra_power 759
> actor1 received less than it's max_power, it require extra_actor_power 395
> actor2 received less than it's max_power, it require extra_actor_power 365
> actor1 and actor2 require the total capped_extra_power 760
>
> using division in re-divvying up power
> actor1 would actually get the extra_actor_power 394
> actor2 would actually get the extra_actor_power 364
>
> if using round the division in re-divvying up power
> actor1 would actually get the extra_actor_power 394
> actor2 would actually get the extra_actor_power 365
>
> Signed-off-by: Jeson Gao <jeson.gao@unisoc.com>
> ---
> drivers/thermal/gov_power_allocator.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/thermal/gov_power_allocator.c b/drivers/thermal/gov_power_allocator.c
> index 92acae53df49..2802a0e13c88 100644
> --- a/drivers/thermal/gov_power_allocator.c
> +++ b/drivers/thermal/gov_power_allocator.c
> @@ -374,9 +374,11 @@ static void divvy_up_power(u32 *req_power, u32 *max_power, int num_actors,
> */
> extra_power = min(extra_power, capped_extra_power);
> if (capped_extra_power > 0)
> - for (i = 0; i < num_actors; i++)
> - granted_power[i] += (extra_actor_power[i] *
> - extra_power) / capped_extra_power;
> + for (i = 0; i < num_actors; i++) {
> + u64 extra_range = (u64)extra_actor_power[i] * extra_power;
> + granted_power[i] += DIV_ROUND_CLOSEST_ULL(extra_range,
> + capped_extra_power);
> + }
> }
>
> static int allocate_power(struct thermal_zone_device *tz,
>
Make sense. There is already DIV_ROUND_CLOSEST_ULL() in that function,
so let's align both. There might be a bit overhead on 32bit machines,
but IPA polling isn't so often there.
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Regards,
Lukasz
next prev parent reply other threads:[~2021-03-15 9:51 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-15 8:25 [PATCH] thermal: power_allocator: using round the division when re-divvying up power gao.yunxiao6
2021-03-15 9:51 ` Lukasz Luba [this message]
2021-03-16 13:15 ` Daniel Lezcano
2021-03-16 13:16 ` Lukasz Luba
2021-03-17 11:20 ` gao yunxiao
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