Linux-kernel mailing list archive 1998-10,: Re: 2.1.89 broken?

# Re: 2.1.89 broken?

Scott Lampert (fortunato@heavymetal.org)
Wed, 11 Mar 1998 08:35:52 -0500 (EST)

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On 11-Mar-98 Rik van Riel wrote:
> When you just grab random disk cache memory, that piece
> of data might be needed again, and has to be reread from
> the (spread-out) filesystem.
> Swapping, OTOH, is done in a clustered way (less seek-time)
> on a small part of the disk (still less seek-time).
>
> I would be interested though, in the partition layout of
> the people who saw worse/better performance:
> begin end
> worse: data sys data swap
> better: data swap sys data
> ???

In my particular case, data, sys and swap are all on separate hard
disks. The swap partition shares a drive which I use for archiving so it
sees little use and for all intents and purposes is its own disk.

> Maybe something like this could explain the difference.
> Personally, when I switched from swap at the far end of
> the disk to swap in the middle (somewhere autumn '95) I
> saw a _HUGE_ improvement.
> Now, I tend to tune my stuff for swap-in-the-middle situations,
> since I only have swap-in-the-middle as a test situation (and
> who wants to run with slow swap anyway?).
>
> If this explains the difference, I'll fix it by making
> page-aging tunable for the following categories:
> - user pages
> - cache pages
> - buffer pages
> - shared pages (?)

I like that last idea, however I think the big problem is the
amount of data the kernel transfers to swap at once - like megs and megs
in one shot. The system freezes pretty hard during these massive swap
phases.
-Scott

    ---
    Scott Lampert              | Home Page: http://www.heavymetal.org
    <fortunato@heavymetal.org> | PGP Key: finger fortunato@heavymetal.org
    "Black holes are where God +-----------------------------------------
       divided by zero."

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