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* src/insdel.c (make_gap): Increase enough to avoid O(N^2) behavior.

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This commit is contained in:
Stefan Monnier 2017-02-19 13:12:16 -05:00
parent f03d936cd7
commit 5c1ebfc504
1 changed files with 14 additions and 1 deletions
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15
src/insdel.c
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@ -560,7 +560,20 @@ void
make_gap (ptrdiff_t nbytes_added)
{
if (nbytes_added >= 0)
make_gap_larger (nbytes_added);
/* With set-buffer-multibyte on a large buffer, we can end up growing the
* buffer *many* times. Avoid an O(N^2) behavior by increasing by an
* amount at least proportional to the size of the buffer.
* On my test (a 223.9MB zip file on a Thinkpad T61):
* With /5 => 24s
* With /32 => 25s
* With /64 => 26s
* With /128 => 28s
* With /1024 => 51s
* With /4096 => 131s
* With /∞ => gave up after 858s
* Of couse, ideally we should never call set-buffer-multibyte on
* a non-empty buffer (e.g. use buffer-swa-text instead). */
make_gap_larger (max (nbytes_added, (Z - BEG) / 64));
#if defined USE_MMAP_FOR_BUFFERS || defined REL_ALLOC || defined DOUG_LEA_MALLOC
else
make_gap_smaller (-nbytes_added);