Re: [uml-devel] ubd is slow. I want to try fixing it

[Артём Л. <the...@gm...>]

Ah, thanks.
I rebuilt it with sync off, and the performance jumped up to something
close to the host one.
Would that actually put ext4 guest fs in any danger in case of a crash?

Sadly, it developed that the 64bit UML can't run 32bit programs, which
is a deal breaker to me.
While it's something that was working at one point and apparently also
fixable with some effort, the sum total of problems makes qemu-kvm
look more attractive in the end.

It's peculiar to see UML in such a state of disrepair - for a long
while i thought it was a widely used lean virtualization platform,
powering things like containers, docker and so on.
Some research and disillusionment later, i'm left wondering what went wrong.
Even the ultra-useful Windows port, CoLinux, seems to be abandoned.

In any case, good luck with the patches!


> 2016-07-09 1:15 GMT+03:00  <use...@li...>:
> Check if you have sync turned on.
>
> Form of async IO - very similar to what posix async IO implementations
> do. If done correctly it can speed up things quite a bit. For it however
> actual files need to be opened async. The number you quoted makes me
> think you have sync enabled (it is enabled in some distros by default
> via kernel config options).