[SOLVED] iotop : CONFIG_TASK_DELAY_ACCT not enabled in kernel

Mark Pettit · 02-15-2022, 02:40 AM

CONFIG_TASK_DELAY_ACCT not enabled in kernel, cannot determine SWAPIN and IO %

iotop is a pretty useful tool. But with the current (compact) kernel the above message is displayed. And it corrupts the screen output too. So request to Pat to consider enabling it at next kernel build in the new current tree.

drumz · 02-15-2022, 10:33 AM

It is enabled on Slackware 15.0:

Code:

$ grep TASK_DELAY_ACCT /boot/config*
/boot/config:CONFIG_TASK_DELAY_ACCT=y
/boot/config-generic-5.15.19.x64:CONFIG_TASK_DELAY_ACCT=y
/boot/config-huge-5.15.19.x64:CONFIG_TASK_DELAY_ACCT=y

Edit: it's also enabled on Slackware 14.2:

Code:

$ grep TASK_DELAY_ACCT /boot/config*
/boot/config:CONFIG_TASK_DELAY_ACCT=y
/boot/config-generic-4.4.276.x64:CONFIG_TASK_DELAY_ACCT=y
/boot/config-generic-4.4.301.x64:CONFIG_TASK_DELAY_ACCT=y
/boot/config-huge-4.4.276.x64:CONFIG_TASK_DELAY_ACCT=y
/boot/config-huge-4.4.301.x64:CONFIG_TASK_DELAY_ACCT=y

Where did you get your kernel?

2nd edit: ... and it's also enabled on Slackware current:

Code:

$ grep TASK_DELAY_ACCT *
config-generic-5.16.9:CONFIG_TASK_DELAY_ACCT=y
config-generic-5.16.9.x64:CONFIG_TASK_DELAY_ACCT=y
config-generic-smp-5.16.9-smp:CONFIG_TASK_DELAY_ACCT=y
config-huge-5.16.9:CONFIG_TASK_DELAY_ACCT=y
config-huge-5.16.9.x64:CONFIG_TASK_DELAY_ACCT=y
config-huge-smp-5.16.9-smp:CONFIG_TASK_DELAY_ACCT=y

What version of Slackware are you running? What kernel version are you running?

3rd edit: I realized your actual question is about iotop. I have it installed and tested it and it runs fine on both Slackware 14.2 and 15.0.

Mark Pettit · 02-15-2022, 12:25 PM

I am not running the huge kernel - I'm using the one that requires the initrd. But I am on the 15.0 version.

uname -a
Linux x1carbon.xxx 5.15.19 #1 SMP PREEMPT Wed Feb 2 01:50:51 CST 2022 x86_64 Intel(R) Core(TM) i7-8550U CPU @ 1.80GHz GenuineIntel GNU/Linux

iotop --version
iotop 0.6

iotop was built from ponce's sbo repo

drumz · 02-15-2022, 01:08 PM

Can you check:

Code:

$ cat /proc/sys/kernel/task_delayacct

You might have to:

Code:

# echo 1 > /proc/sys/kernel/task_delayacct

See https://github.com/Tomas-M/iotop/issues/21

TheRealGrogan · 02-15-2022, 01:31 PM

Even when set to Y in kernel config, it's disabled by default. It doesn't seem to work to set it on the fly either with echo 1, and if you use the sysctl only processes started after will be accounted.

Append "delayacct" to the kernel command line.

https://www.kernel.org/doc/html/late...ccounting.html

Code:

Usage

Compile the kernel with:

CONFIG_TASK_DELAY_ACCT=y
CONFIG_TASKSTATS=y

Delay accounting is disabled by default at boot up. To enable, add:

delayacct

to the kernel boot options. The rest of the instructions below assume this has been done. Alternatively, use sysctl kernel.task_delayacct to switch the state at runtime. Note however that only tasks started after enabling it will have delayacct information.

P.S. I should say that I use iotop and all my kernels have the delayacct parameter appended. I can neither quantify nor qualify any performance hit from accounting overhead.

bassmadrigal · 02-15-2022, 02:32 PM

In reading online, it seems like this might be an issue in iotop not detecting any sysctl changes. So even though delayacct might have been enabled via sysctl, the iotop on SBo doesn't detect that change. In the github issue linked, it seems that it might be tied to the python version of iotop (which is what SBo uses), but the repo in the linked bug report is apparently a c version that supposedly has the fix.

It might be worth looking into switching the python iotop on SBo to the C version of iotop as that has been continually updated (had a release 19 days ago) whereas the 0.6 python version was released 8 years ago (although, there is some git activity that could eventually turn into a release).

Maybe someone on 15.0 can check by building the c version of iotop and see if it works (I'm running an older kernel without the issue, so I can't check). Apparently some distros distribute both versions and call the C version iotop-c, but if the python version is effectively broken, I imagine we should probably just replace it with the ported version.

Mark Pettit · 02-15-2022, 10:47 PM

$ cat /proc/sys/kernel/task_delayacct printed a 0

After running this : echo 1 > /proc/sys/kernel/task_delayacct
the iotop produced no error messages at all.

I will mark this as solved, but as usual 'bassmadrigal' has added some great insight. Thanks to 'drumz' as well.