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| author | Davide Libenzi <davidel@xmailserver.org> | 2008-11-07 21:24:33 -0800 |
|---|---|---|
| committer | Junio C Hamano <gitster@pobox.com> | 2008-12-02 23:45:37 -0800 |
| commit | 733070bea9ce28d557f0b0950acc05b3fe6ff6c6 (patch) | |
| tree | 4bfc97b38f65e30f28ac296a392d1cf85b36313a | |
| parent | 0fd9d7e66deb7071da2a568b96c94f94ee890908 (diff) | |
| download | git-733070bea9ce28d557f0b0950acc05b3fe6ff6c6.tar.gz | |
xdiff: give up scanning similar lines early
In a corner case of large files whose lines do not match uniquely, the
loop to eliminate a line that matches multiple locations adjacent to a run
of lines that do not uniquely match wasted too much cycles. Fix this by
giving up early after scanning 100 lines in both direction.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
| -rw-r--r-- | xdiff/xprepare.c | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/xdiff/xprepare.c b/xdiff/xprepare.c index e87ab57c65..a43aa72cd0 100644 --- a/xdiff/xprepare.c +++ b/xdiff/xprepare.c @@ -23,10 +23,9 @@ #include "xinclude.h" - #define XDL_KPDIS_RUN 4 #define XDL_MAX_EQLIMIT 1024 - +#define XDL_SIMSCAN_WINDOW 100 typedef struct s_xdlclass { @@ -313,6 +312,18 @@ static int xdl_clean_mmatch(char const *dis, long i, long s, long e) { long r, rdis0, rpdis0, rdis1, rpdis1; /* + * Limits the window the is examined during the similar-lines + * scan. The loops below stops when dis[i - r] == 1 (line that + * has no match), but there are corner cases where the loop + * proceed all the way to the extremities by causing huge + * performance penalties in case of big files. + */ + if (i - s > XDL_SIMSCAN_WINDOW) + s = i - XDL_SIMSCAN_WINDOW; + if (e - i > XDL_SIMSCAN_WINDOW) + e = i + XDL_SIMSCAN_WINDOW; + + /* * Scans the lines before 'i' to find a run of lines that either * have no match (dis[j] == 0) or have multiple matches (dis[j] > 1). * Note that we always call this function with dis[i] > 1, so the |