Re: Linux VM subsystem (Was: Big mallocs, mmap sorrows and double buffering.)

Ingo Molnar (mingo@pc5829.hil.siemens.at)
Wed, 12 Feb 1997 18:20:04 +0100 (MET)


On Wed, 12 Feb 1997, A.N.Kuznetsov wrote:

> 1. Allocate huge memory area. (I used 56-250Mb for systems
> with 64Mb of physical memory)
> 2. Then you dirtify this pages starting from beginning,
> not very fastly (without swapping it should take ~5min for
> P-133 and length 100Mb) Really, it is just array of
> n*n matrices, when n=160-250, and pass consists in
> matrix multiplications, so that it scales as n^3.
> 3. Then you repeat this procedure in backward direction,
> this pass scales as n.
>
> The statement is that other unices make this procedure
> without pain, time grows almost linearly, and when running
> with low priority in background it practically does not hamper other users.
> Linux time grows EXPONENTIALLY after starting swap [...]

i remember Linus commenting on such issues about a year ago. He proposed
some code, and told people to send patches to him.

what do you want more? I certainly wont code it up as nothing in my
machine wants to invert matrices bigger than 1x1 ;)

[/flame on]

so instead of making (imho quite offensive) comments about the Linux VM
manager, what about starting to hack it? Should be one night or two, as
the Linux VM manager is coded in a >brilliant< way IMHO.

-- mingo