Re: [PATCH 00/23] per device dirty throttling -v8

Linus Torvalds
2007-08-04T16:15:24Z

On Sat, 4 Aug 2007, Ingo Molnar wrote:
>
> i forgot this entry:
>
> " We recently upgraded our office to gigabit Ethernet and got some big
> AMD64 / 3ware boxes for file and vmware servers... only to find them
> almost useless under any kind of real load. I've built some patched
> 2.6.21.6 kernels (using the bdi throttling patch you mentioned) to
> see if our various Debian Etch boxes run better. So far my testing
> shows a *great* improvement over the stock Debian 2.6.18 kernel on
> our configurations. "

Well, quite frankly, there are other changes between 2.6.18 and 2.6.21
that are more likely to be a big deal than Peter's patches. No offense to
Peter, but we also cut the default dirty percentage by a factor of four in
that timeframe, and that made a *huge* difference for some setups (and
admittedly not so much on others ;)

> and bdi has been in -mm in the past i think, so we also know (to a
> certain degree) that it does not hurt those workloads that are fine
> either.

Hey, I'm not complaining. I think the code looks fine. I just want to make
sure that it actually helps.

> [ my personal interest in this is the following regression: every time i
> start a large kernel build with DEBUG_INFO on a quad-core 4GB RAM box,
> i get up to 30 seconds complete pauses in Vim (and most other tasks),
> during plain editing of the source code. (which happens when Vim tries
> to write() to its swap/undo-file.) ]

So do the patches really end up helping your case? Or is this just why
you're following it, and hoping they'll eventually do so?

Linus