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    SubjectRe: Swappiness vs. mmap() and interactive response
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    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:

    http://lkml.org/lkml/2007/7/21/219




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