"Martin J. Bligh" <mbligh@aracnet.com> wrote:
>
> > . I got tired of the objrmap code going BUG under stress, so it is now in
> > disgrace in the experimental/ directory.
>
> Any chance of some more info on that? BUG at what point in the code,
> and with what test to reproduce?
A bash-shared-mapping (from ext3 CVS) will quickly knock it over. It gets
its PageAnon/page->mapping state tangled up.
Must confess that I have trouble getting excited over objrmap. It introduces
- inconsistency (pte_chains versus vma-list scanning)
- code complexity
- a quadratic search
- nasty, nasty problems with remap_file_pages(). I'd rather not have to
nobble remap_file_pages() functionality for this reason.
and what do we gain from it all? The small fork/exec boost isn't very
significant. What we gain is more lowmem space on
going-away-real-soon-now-we-sincerely-hope highmem boxes.
Ingo-rmap seems a better solution to me. It would be a fairly large change
though - we'd have to hold the four atomic kmaps across an entire pte page
in copy_page_range(), for example. But it will then have good locality of
reference between adjacent pages and may well be quicker than pte_chains.
-
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This archive was generated by hypermail 2b29 : Wed Apr 23 2003 - 22:00:38 EST