Arch Linux

lilmike

Member

Registered: 2014-09-25

Posts: 26

djb2 process using tons of throughput?

Hi,
I will sometimes get a notification from my server (through munin) that my disk wait time is high (like 3-4 seconds). I looked into it, and my host (chunkhost) says that my vps is one of the top users of io on this particular server. Looking more into it, I found that the djb2 process is using up to 50-60 MB/s every 5-10 seconds, causing the hypervisor to throttle my disk io. I found that djb2 is responsible for journaling on the filesystem, so looked how to minimize its footprint.
One thing I found said I could modify /etc/fstab to disable journaling, but when I did that, my filesystem mounted read only on reboot, presumably because of a filesystem error. So, after reverting to a backup, I tried disabling the journal with tune2fs, but that was not possible because I could not mount my filesystem read only, due to the fact it was always busy, and I can't boot into a live environment because it's a vps. So now here I am, and here's my question:
How can I reduce the disk throughput of djb2 without disabling the journal, or if I have to, how can I do it without making my filesystem read only or booting into a live environment?
A little more information: I run nginx, php-fpm, hhvm, maria db, and a few more servers on this vps, so I think I can see why djb2 is running so much, I just can't figure out how to curb the resource usage.
Thanks,
-Michael.

lilmike

Member

Registered: 2014-09-25

Posts: 26

Re: djb2 process using tons of throughput?

*bump*
Still having this issue, any ideas?
-Michael.

lilmike

Member

Registered: 2014-09-25

Posts: 26

Re: djb2 process using tons of throughput?

Hi,
I still haven't been able to figure this out.
-Michael.

Lone_Wolf

Administrator

From: Netherlands, Europe

Registered: 2005-10-04

Posts: 13,125

Re: djb2 process using tons of throughput?

I found that djb2 is responsible for journaling on the filesystem, so looked how to minimize its footprint.

All i can find about djb2 refers to a hash-function, don't think that's what is causing you trouble.

Could you link to that info ?
What filesystems are you using, please post the fstab ?

Last edited by Lone_Wolf (2015-11-26 13:15:11)

---

Disliking systemd intensely, but not satisfied with alternatives so focusing on taming systemd.

clean chroot building not flexible enough ?
Try clean chroot manager by graysky

Durden

Member

Registered: 2011-06-19

Posts: 261

Re: djb2 process using tons of throughput?

Need more info

1) How did you determine this process had anything to do with the filesystem?
2) Are you sure its djb2 and not db2?
3) What filesystem are you using?

lilmike

Member

Registered: 2014-09-25

Posts: 26

Re: djb2 process using tons of throughput?

Hi,
I found it under sudo iotop, and it would pop up to the top every so often.
I believe it was djb2/dev/xvda1-8 or something similar.

I'm using ext4. I will post the fstab in a bit when I can get on my server.
-Michael.