Re: Scrolling huge buffers and cc-mode

[Dmitry Antipov <dmantipov@yandex.ru>]

It looks like the reason of slow scrolling is how the C++ namespaces are handled.

Basically my test file is:

namespace X {
namespace Y {

/* 13K lines of code */

} }

/* middle-point */

namespace X {
namespace Y {

/* 13K lines of code */

} }

When scrolling reaches middle-point, everything hangs, most probably because
we need to scan huge regions (first and second namespace blocks). When I remove
all namespace definitions (with matched '}'), scrolling works much faster.
Corresponding profile is:

     13.04%        emacs  emacs                          [.] mark_object
      7.70%        emacs  emacs                          [.] exec_byte_code
      6.79%        emacs  emacs                          [.] re_match_2_internal
      6.48%        emacs  emacs                          [.] lookup_char_property
      4.70%        emacs  emacs                          [.] scan_sexps_forward
      4.67%        emacs  emacs                          [.] Fgarbage_collect
      4.62%        emacs  emacs                          [.] re_compile_pattern
      4.57%        emacs  emacs                          [.] next_interval
      3.29%        emacs  emacs                          [.] find_interval
      3.16%        emacs  emacs                          [.] mark_interval
      2.15%        emacs  emacs                          [.] Fcdr
      2.06%        emacs  emacs                          [.] update_syntax_table
      1.83%        emacs  emacs                          [.] Flocal_variable_p
      1.33%        emacs  emacs                          [.] Fassq
      1.19%        emacs  emacs                          [.] balance_intervals_internal
      1.13%        emacs  emacs                          [.] Ffuncall
      1.00%        emacs  emacs                          [.] compile_pattern

This is very similar to what I'm seeing while scrolling over xdisp.c:

     13.92%        emacs  emacs                          [.] mark_object
      8.20%        emacs  emacs                          [.] exec_byte_code
      4.91%        emacs  emacs                          [.] re_match_2_internal
      4.78%        emacs  emacs                          [.] Fgarbage_collect
      4.65%        emacs  emacs                          [.] lookup_char_property
      3.60%        emacs  emacs                          [.] find_interval
      3.55%        emacs  emacs                          [.] scan_sexps_forward
      3.45%        emacs  emacs                          [.] re_compile_pattern
      2.77%        emacs  emacs                          [.] Flocal_variable_p
      2.71%        emacs  emacs                          [.] mark_interval
      2.46%        emacs  emacs                          [.] next_interval
      1.62%        emacs  emacs                          [.] update_syntax_table
      1.52%        emacs  emacs                          [.] Fassq
      1.45%        emacs  emacs                          [.] Fcdr
      1.35%        emacs  emacs                          [.] Ffuncall
      1.11%        emacs  emacs                          [.] compile_pattern

Dmitry