Re: Swappiness vs. mmap() and interactive response

Peter Zijlstra
2009-04-28T08:11:58Z

On Tue, 2009-04-28 at 13:28 +0530, Balbir Singh wrote:
> On Tue, Apr 28, 2009 at 1:18 PM, Peter Zijlstra <peterz@infradead.org> wrote:
> > On Tue, 2009-04-28 at 14:35 +0900, KOSAKI Motohiro wrote:
> >> (cc to linux-mm and Rik)
> >>
> >>
> >> > Hi,
> >> >
> >> > So, I just set up Ubuntu Jaunty (using Linux 2.6.28) on a quad core phenom box,
> >> > and then I did the following (with XFS over LVM):
> >> >
> >> > mv /500gig/of/data/on/disk/one /disk/two
> >> >
> >> > This quickly caused the system to. grind.. to... a.... complete..... halt.
> >> > Basically every UI operation, including the mouse in Xorg, started experiencing
> >> > multiple second lag and delays. This made the system essentially unusable --
> >> > for example, just flipping to the window where the "mv" command was running
> >> > took 10 seconds on more than one occasion. Basically a "click and get coffee"
> >> > interface.
> >>
> >> I have some question and request.
> >>
> >> 1. please post your /proc/meminfo
> >> 2. Do above copy make tons swap-out? IOW your disk read much faster than write?
> >> 3. cache limitation of memcgroup solve this problem?
> >> 4. Which disk have your /bin and /usr/bin?
> >>
> >
> > FWIW I fundamentally object to 3 as being a solution.
> >
>
> memcgroup were not created to solve latency problems, but they do
> isolate memory and if that helps latency, I don't see why that is a
> problem. I don't think isolating applications that we think are not
> important and interfere or consume more resources than desired is a
> bad solution.

So being able to isolate is a good excuse for poor replacement these
days?

Also, exactly because its isolated/limited its sub-optimal.

> > I still think the idea of read-ahead driven drop-behind is a good one,
> > alas last time we brought that up people thought differently.
>
> I vaguely remember the patches, but can't recollect the details.

A quick google gave me this: