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Date: Sat, 12 Oct 2024 18:10:30 -0700
From: Stephen Hemminger <stephen@networkplumber.org>
To: Huisong Li <lihuisong@huawei.com>
Cc: <dev@dpdk.org>, <mb@smartsharesystems.com>, <thomas@monjalon.net>,
<ferruh.yigit@amd.com>, <anatoly.burakov@intel.com>,
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<david.marchand@redhat.com>, <fengchengwen@huawei.com>,
<liuyonglong@huawei.com>
Subject: Re: [PATCH v10 1/2] power: introduce PM QoS API on CPU wide
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In-Reply-To: <20240912023812.30885-2-lihuisong@huawei.com>
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Errors-To: dev-bounces@dpdk.org
On Thu, 12 Sep 2024 10:38:11 +0800
Huisong Li <lihuisong@huawei.com> wrote:
> +
> +PM QoS
> +------
> +
> +The deeper the idle state, the lower the power consumption, but the longer
> +the resume time. Some service are delay sensitive and very except the low
> +resume time, like interrupt packet receiving mode.
> +
> +And the "/sys/devices/system/cpu/cpuX/power/pm_qos_resume_latency_us" sysfs
> +interface is used to set and get the resume latency limit on the cpuX for
> +userspace. Each cpuidle governor in Linux select which idle state to enter
> +based on this CPU resume latency in their idle task.
> +
> +The per-CPU PM QoS API can be used to set and get the CPU resume latency based
> +on this sysfs.
> +
> +The ``rte_power_qos_set_cpu_resume_latency()`` function can control the CPU's
> +idle state selection in Linux and limit just to enter the shallowest idle state
> +to low the delay of resuming service after sleeping by setting strict resume
> +latency (zero value).
> +
> +The ``rte_power_qos_get_cpu_resume_latency()`` function can get the resume
> +latency on specified CPU.
> +
These paragraphs need some editing help. The wording is awkward,
it uses passive voice, and does not seemed directed at a user audience.
If you need help, a writer or AI might help clarify.
It also ends up in the section associated with Intel UnCore.
It would be better after the Turbo Boost section.
> + ret = open_core_sysfs_file(&f, "w", PM_QOS_SYSFILE_RESUME_LATENCY_US, lcore_id);
> + if (ret != 0) {
> + POWER_LOG(ERR, "Failed to open "PM_QOS_SYSFILE_RESUME_LATENCY_US, lcore_id);
> + return ret;
> + }
The function open_core_sysfs_file() should have been written to return FILE *
and then it could have same attributes as fopen().
The message should include the error reason.
if (open_core_sysfs_file(&f, "w", PM_QOS_SYSFILE_RESUME_LATENCY_US, lcore_id)) {
POWER_LOG(ERR, "Failed to open " PM_QOS_SYSFILE_RESUME_LATENCY_US ": %s",
lcore_id, strerror(errno));