Re: "kworker" writes to disc every 5 seconds on battery

[Marty <martyb@ix.netcom.com>]

On 10/18/2014 04:47 PM, Teresa e Junior wrote:
> Hello! I have noticed that my current setup of Chrome writes to disc
> every second. While hunting for the problem, I have found an old bug
> report on Google Code about this, and from my tests I concluded my
> solution for now would be to run Chrome with its profile and cache in a
> tmpfs. Problem solved, or rather, not solved at all.
>
> In a laptop running on battery, it would be desirable to let the HD spin
> down a bit sometimes, right, right, right? Well, I think so, so after
> optimizing the settings for some applications, I have found these two
> spoiled brats who write to the disc frequently, and never let it sleep:
> jbd2/sda3-8 and kworker/u8:0.
>
> The jbd2/sda3-8 problem seems to have been solved by remounting the
> partition with commit=60, so no more journal writes every five seconds.
>
> But what about this kworker/u8:0 lad? Who is he, and what is he doing? I
> know it is a kernel worker, but not more than this. After some search, I
> found someone saying I should run: `echo l | sudo tee
> /proc/sysrq-trigger', which outputs some nice information, but which I
> could not understand. So I have asked my mother, because she was the
> person who taught me how to walk, if she could read it, and was left
> puzzled as to how there could be something even our ancestors couldn't
> understand.

They understood once, as students, but then it got too big and 
complicated, and they didn't have time to keep up. They forgot to KISS (qv).

Try looking for everyone with the same problems with the laptop model 
and electronics, and remember that most laptops are designed for 
Windows, which often makes it hard to solve problems like yours.

> Is there a way for me to know what is kworker/u8:0 writing to the disc

A printk in the kworker thread? but be careful, may need mom's help with 
that.

> every five seconds? Also, if it's not a bother, could someone test if
> this also happens there? The commands I run while on battery were:
>
> echo 1 | sudo tee /proc/sys/vm/block_dump
> tail -F /var/log/debug | grep -v dirtied
> echo 0 | sudo tee /proc/sys/vm/block_dump
>
> And by the way, my kernel is 3.15.10-zen-686-pae
>
> Thank you!
> Teresa e Junior