On Wed, Jan 09, 2008 at 11:31:38PM -0800, Nishanth Aravamudan wrote:
> On 10.01.2008 [16:01:11 +1100], David Gibson wrote:
> > On Tue, Jan 08, 2008 at 09:07:57PM -0800, Nishanth Aravamudan wrote:
> > > For larger databases, users often only want their text to be placed in
> > > hugepages. libhugetlbfs does not currenlty provide this mode, however,
> > > so users have been working around it in ... odd ... ways. Add explicit
> >
> > I still don't really understand how you can get a program with text so
> > enormous it will benefit but data which won't, but there you go.
>
> Well, I *think* it's more that they are sharing the text, so really the
> benefit comes from the hugepages being shared by all the programs. But
> the cost of using hugepage data nullifies it. That's my understanding,
> at least.
Except that if they were using normal pages, the text would just be
mmap()ed from disk and so should be shared anyway.
> > > support for T-only relinking via new linker scripts for ppc64, x86 and
> > > x86_64. Unfortunately, I do not think (with my knowledge, at least) that
> > > ppc32 can support T-only, due to the limitation that the PLT must be
> > > within 32M of the text segment, confirmed in testing and based upon the
> > > comment in the elf32ppclinux.xBDT:
> >
> > It might be possible to do this by having a mini-data segment in
> > hugepages near the text segment, containing just the PLT, with the
> > rest of the data segment and BSS back in normal pages.
>
> I think Adam is encountering a problem with glibc where the text, data
> and BSS are not continuous (64-bit B-linker script). This leads to odd
> failures when libraries get mapped in between the segments. I would
> worry that would happen here too... But it's a good idea and I can try
> testing it out.
Ah. Yuck.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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