the "vm_mm->mm" was of course a typo and should be read as
"vma->vm_mm". Sorry.
On Thu, 7 Sep 2000, Tigran Aivazian wrote:
> On Thu, 7 Sep 2000, Tigran Aivazian wrote:
>
> > On Thu, 7 Sep 2000, Linus Torvalds wrote:
> >
> > >
> > >
> > > On Thu, 7 Sep 2000, Tigran Aivazian wrote:
> > > >
> > > > k) all swapout functions in mm/vmscan.c can be optimized by removing 'mm'
> > > > argument. This part was reviewed by Rick van Riel and approved.
> > >
> > > But they then get "mm" themselves anyway.
> > >
> > > What's the point? With argument passing, on certain architectures it stays
> > > in registers. On other architectures it is in memory on the stack, but
> > > that's not slower than accessing it from memory off another pointer.
> > >
> > > Linus
> >
> > Linus, I am sorry to say this (because I know you are busy) but it would
> > appear you didn't look at the patch (that part of it). The patch does the
> > right thing, I believe, but my description was too brief.
> >
> > If you look at those functions you will see that they sometimes access
> > 'mm' via argument and sometimes via vm_mm->mm - this is a complete mess so
> > my patch tidies it up a bit.
> >
> > In other words, if that 'mm' is available via vm_mm->mm there is no point
> > in passing it on the stack. Or if we pass it on the stack, there is no
> > point accessing it via vm_mm->mm. See my point now?
>
> in case, even this is too brief, here is more:
>
> ... so, I had a choice between:
>
> a) remove 'mm' argument
>
> or
>
> b) make all access to 'mm' go via this 'mm' argument
>
> and I thought removing the argument, i.e. choice a) was better than b).
>
> And, yes, I do understand how arguments are passed and what gcc can do
> about it.
>
> Regards,
> Tigran
>
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