Re: Scrolling huge buffers and cc-mode

[Dmitry Antipov]

On 12/18/2012 11:58 PM, Stefan Monnier wrote:

> > about 1 minute is below.  If I understand correctly, it blames
> > scan-sexps for most of the CPU load.
>
> Indeed, but running scan-sexps on the whole buffer doesn't take that
> long, so the problem is not that scan-sexps is slow, but that it's
> called too many times.

I didn't try to profile elisp, but here is what I'm seeing at the lower level.
Since the percentage of exec_byte_code is just 1.21%, I suspect that elisp
is not a bottleneck here. Looking at enormous percentage of lookup_char_property
and next_interval, I would rather suspect an issue with interval trees.

Dmitry

# ========
# captured on: Tue Dec 18 19:30:31 2012
# hostname : localhost.localdomain
# os release : 3.6.10-2.fc17.x86_64
# perf version : 3.6.10-2.fc17.x86_64
# arch : x86_64
# nrcpus online : 4
# nrcpus avail : 4
# cpudesc : Intel(R) Core(TM) i5-2410M CPU @ 2.30GHz
# cpuid : GenuineIntel,6,42,7
# total memory : 3930292 kB
# cmdline : /usr/bin/perf record -e stalled-cycles-frontend -e 
stalled-cycles-backend -F 10000 ./src/emacs -Q ../../misc/huge.cc
# event : name = stalled-cycles-frontend, type = 0, config = 0x7, config1 = 
0x0, config2 = 0x0, excl_usr = 0, excl_kern = 0, excl_host
# event : name = stalled-cycles-backend, type = 0, config = 0x8, config1 = 0x0, 
config2 = 0x0, excl_usr = 0, excl_kern = 0, excl_host
# HEADER_CPU_TOPOLOGY info available, use -I to display
# HEADER_NUMA_TOPOLOGY info available, use -I to display
# ========
#
# Samples: 3M of event 'stalled-cycles-frontend'
# Event count (approx.): 284964331659
#
# Overhead      Command                  Shared Object                          
                        Symbol
# ........  ...........  .............................  
......................................................
#
    22.65%        emacs  emacs                          [.] lookup_char_property
    21.21%        emacs  emacs                          [.] scan_sexps_forward
    17.65%        emacs  emacs                          [.] next_interval
     8.29%        emacs  emacs                          [.] Fcdr
     4.66%        emacs  emacs                          [.] update_syntax_table
     2.15%        emacs  emacs                          [.] scan_lists
     1.95%        emacs  emacs                          [.] mark_object
     1.92%        emacs  emacs                          [.] update_interval
     1.74%        emacs  emacs                          [.] Fassq
     1.41%        emacs  emacs                          [.] back_comment
     1.38%        emacs  emacs                          [.] forw_comment
     1.21%        emacs  emacs                          [.] exec_byte_code
     1.08%        emacs  emacs                          [.] char_quoted
     1.05%        emacs  emacs                          [.] re_match_2_internal
     0.70%        emacs  emacs                          [.] re_compile_pattern
     0.67%        emacs  emacs                          [.] Fgarbage_collect
     0.58%        emacs  emacs                          [.] find_interval