Hi Stephen,
Can you take a look at this reply so as to send out the next version ASAP?
Thanks.😁
/Huisong
在 2024/10/14 20:19, lihuisong (C) 写道:
Hi Stephen,
在 2024/10/13 9:10, Stephen Hemminger 写道:
On Thu, 12 Sep 2024 10:38:11 +0800
Huisong Li <lihuis...@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.
How about the following description:
-->
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 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.
The ``rte_power_qos_set_cpu_resume_latency()`` and
``rte_power_qos_get_cpu_resume_latency()``
can set and get the CPU resume latency based on this per-CPU sysfs.
The ``rte_power_qos_set_cpu_resume_latency()`` can control the CPU's
idle state selection and limit to enter the shallowest idle state
to low the delay of resuming service by setting strict resume
latency (zero value) so as to get better performance.
It also ends up in the section associated with Intel UnCore.
It would be better after the Turbo Boost section.
Ack
+ 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().
Do you mean we should save this handle for directly using it to get or
set this resume latency?
If it is I understand, we cannot do it like this. Because qos driver
in Linux use the "noop_llseek()" as the .llseek API.
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));
Good idea. Thanks.
.
