Messages in this thread | | | Date | Wed, 23 Apr 2003 14:46:48 -0700 | From | Andrew Morton <> | Subject | Re: 2.5.68-mm2 |
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"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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