High load average in OpenWrt 18 /19 on mt7688an

Alisaeed1 · December 6, 2019, 2:37pm

Hi
I have a problem with Openwrt 18 /Openwrt 19. when I check load average with uptime command, often the result is more 0.6 .I checked the CPU with htop but I do not see any process more 2%. meantime, when I check the load average , luci is not used.
But on LEDE 17,load average is low, it is about 0.1 and is normal for my device, while the situation is quite similar to openwrt 18 / openwrt 19.
please help me in this way,and give me your suggestions to solve this case.
Thanks.

jeff · December 6, 2019, 3:41pm

“Load average” has been discussed as an unreliable measure (for Linux in general). A higher load average may be due to LuCI running. If you SSH in, what does top show for CPU utilization? Is it different with no browser windows open even just connected to the device?

Alisaeed1 · December 6, 2019, 4:49pm

I get load average by ssh using uptime command .
yes, when I test that with open browser windows, the load average is more.
also I test this issue without ruining LuCI, but the load average is high again and it is about 0.6.
Is my CPU (mt7688an-1 core-588MHz) effect on this case(High load average)?

jeff · December 6, 2019, 5:57pm

A MediaTek MT7628 running at under 600 MHz is at the bottom end of performance these days.

Load average doesn't tell much useful. Knowing the average number of threads running and waiting doesn't say much about CPU utilization. See, for example, http://www.brendangregg.com/blog/2017-08-08/linux-load-averages.html

What does top show for CPU utilization?

Edit: This note in the upstream Linux source code might be helpful in allowing you to put less concern on "load average" and more on what the device is actually doing

github.com

torvalds/linux/blob/master/kernel/sched/loadavg.c#L6


// SPDX-License-Identifier: GPL-2.0
/*
 * kernel/sched/loadavg.c
 *
 * This file contains the magic bits required to compute the global loadavg
 * figure. Its a silly number but people think its important. We go through
 * great pains to make it work on big machines and tickless kernels.
 */
#include "sched.h"


/*
 * Global load-average calculations
 *
 * We take a distributed and async approach to calculating the global load-avg
 * in order to minimize overhead.
 *

Alisaeed1 · December 6, 2019, 9:00pm

Thanks jeff, it was an useful paper about the concepts of load average.
You know when I work with LEDE 17.01, the temperature of my device is more cooler than using openwrt 19.
I don't know this case is related to high load average or not.The top result is attached below:

jeff · December 6, 2019, 10:04pm

Looks like you've got a lot running there! It doesn't surprise me that it has significant CPU use on a low-end SoC.

I see at least:

IPSEC-related services
SNMPD
Samba and all its services

These don't look familiar to me and don't seem to be a "normal" part of an OpenWrt distribution:

/root/WiFiController.lua
/root/ResetFactory.lua

Even at a percent or two each, things add up.

Alisaeed1 · December 8, 2019, 6:39am

I found the solution,I'm using UMTS/GPRS/EV-DO protocol for LTE module, when sim card is not present the service is using resource system as more.during sim card present and network is connected everything is OK and my load average is about 0.02.

tmomas · December 18, 2019, 6:39am

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