On Sat, 7 Apr 2007 17:21:38 -0700 (PDT) Christoph Lameter <[email protected]> wrote:
> On Sat, 7 Apr 2007, Andrew Morton wrote:
>
> > Which is all a ton of fun, but this subversion of the architecture's
> > freedom to use volatile, memory barriers etc is a worry. We do the same in
> > page_alloc.c, of course...
>
> I just tried the approach that we discussed earlier and it was not
> nice either.
We've discussed at least three approaches, so we don't know to what you refer.
> Lets just use a page flag please.
Nope, try harder.
PageCompound is an unlikely case. Back in the old days we would have done
if (PageCompound(page))
goto out_of_line;
back:
do_stuff_with(page);
return;
out_of_line:
if (PageTail(page)) {
page = page_tail(page);
goto back;
}
<do other stuff>
and nowadays we hope that gcc does the above for us. If it doesn't do it
for us, perhaps it needs open-coded help.
Because I don't expect there will be much efficiency difference between the
above and the use of another page flag.
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