Can't Change IO Scheduler

[wizard10000]

There doesn't seem to be huge differences in most case, just sometimes. Also, one wins in one place while another wins elsewhere. Illustrates that this is no simple issue. It would be interesting to do a full spectrum of file systems, drive types, and kernel versions.

I went the same route you did; set cfq for spindles and deadline for SSD.

[farukdgn]

Even when I try deadline scheduler, my computer gets really slow when I'm doing some heavy I/O operations. Is this a problem with Linux? I'm not used to experiencing this in Windows. Does Windows make the app on the foreground have a higher priority?

The problem seems really odd to me because even when the contents of the file I'm trying to open should have been in RAM cache by now, they still open too slow. For example, even for Terminal: I open terminal, close it and reopen it but it still makes me wait for a few seconds.

[Snowhog]

Copying huge files 'to where'? On your systems drive, or to an external location, and if the latter, how is that location connected?

[farukdgn]

Copying huge files 'to where'? On your systems drive, or to an external location, and if the latter, how is that location connected?

I experienced slowness while I was files copying from the systems drive to itself, or unzipping something etc. I didn't test other situations.

[Snowhog]

Okay, so when you said 'big files', what size are you talking about?

[farukdgn]

Okay, so when you said 'big files', what size are you talking about?

2 gb+

[jlittle]

This problem has a long and chequered history, because it only affected some systems, and I speculate seemingly didn't hit the kernel developers much, so they seemed to ignore it for years. The underlying cause is explained in this bugzilla comment. Or this LWN article.

The problem tends to baffles people like me that have much experience with thrashing, swapping, systems because it behaves like them, page faulting even when there's no swap at all.

Changing the io scheduler to deadpool avoids the problem for a lot of systems, but not all. You could research the settings in /proc/sys/vm/dirty_* and experiment with changing those. F.ex.

echo $((16*1024*1024)) > /proc/sys/vm/dirty_background_bytes
echo $((48*1024*1024)) > /proc/sys/vm/dirty_bytes

Now another supposed fix is in linux kernel 4.10 which has landed in ubuntu 17.04, "writeback throttling". It is "enabled"; I don't know how to turn it on, or how to see if it is on.

[acheron]

Changing the io scheduler to deadpool

??

[oshunluvr]

LOL, acheron