Re: [PATCH 14/38] Remove struct mm_struct::exe_file et al

From: Andrew Morton
Date: Sun May 31 2009 - 19:51:03 EST

On Sun, 31 May 2009 16:15:50 -0700 (PDT) Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:

> On Sun, 31 May 2009, Andrew Morton wrote:
> >
> > What I always find a bit weird is that an MM container is used as the
> > central point for a number of sched obects. But it's logical, given
> > that the never-before-stated definition of a heavyweight process is
> > "thing which share a VM".
> It has nothing to do with "heavy-weight process" or anything else.
> The thing is, from a scheduling standpoint, one of the primary performance
> concerns in the TLB switch.
> And there's a 1:1 relationship between TLB switch and MM container, modulo
> the issue of kernel tasks (and those obviously "borrow" approproate MM
> structs to avoid the switch).

That's all an obscure performance-oriented internal implementation detail.

> So it's not weird at all. It's very direct, and a very straightforward and
> obvious relationship.

It's arbitrary! If we were to gain more performance benefit by
aggregating processes under, say, the fs_struct then that's the way the
kernel would have been implemented.

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