Re: How much kernel stack do we need?

Mathieu Bouchard (boum01@UQAH.UQuebec.CA)
Sat, 20 Jun 1998 16:42:02 -0400 (EDT)

> > In 2.1.x kernels, the kernel stack size is 8192 bytes (2 pages) on the i386,
> > minus the size of the task structure (around 1000). This means the stack is
> > more than 3000 bytes larger than in 2.0.x where it used to be one page. My
> > question is: do we really need this?
> This is a _very_ good question, since it could save us one
> unswappable page _per process_. This might not seem like
> an awful lot of memory, but with the current fragmentation
> problems this patch could save our butt...
> (at least until the zone allocator is ready)

When I first read this I didn't take it seriously, but if you say that 1.
it's one per process and 2. it's unswappable, then it's definitely
worth it. Imagine something like a webserver trying to fill 2000 requests at
once. just saved 8 MB of unswappable memory. This allows for 100-200 more
requests at once, possibly.

and 3rd reason: it was 4k in v2.0.*; going to 8k is a regression. This is
a word from a once-was asm freak and I had 16k RAM on my first puter.
getting it back to 4k and making further optimisations beyond this will
help making processes more lightweight, which is always a Good Thing (tm)
imho.

Now what is (briefly) the zone allocator? is there any info i can get on
this?

matju

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