Re: [PATCH] Use mmap for symbol tables

[Jim Blandy <jimb at red-bean dot com>]

On 1/30/06, Daniel Jacobowitz <drow@false.org> wrote:
> One important note: you bypassed symfile_relocate_debug_section.
> Instead, this logic ought to live in there; if the debug section
> has relocations, we can't mmap it, because we do need to modify
> everything we read from disk.
>
> There's some benefits other than the obvious to using read-only
> mmap; you'll get better hot-cache performance because two consecutive
> sessions can do DWARF processing on pages already read in, rather than
> memcpy'ing them from the page cache.

When debug sections have relocations, are they really covered with
relocs, or are the relocs rare?  I thought that MAP_PRIVATE was
implemented using copy-on-write pages, so if the relocations are rare,
then MAP_PRIVATE would give you a writeable image that still shared as
much as possible.