On Fri, 13 Aug 2010, Gabor Kovesdan wrote:
Em 2010.08.13. 10:43, Doug Barton escreveu:
My reason is simple, performance. While doing some portmaster work
recently I was regression testing some changes I made to the --index*
options and noticed that things were dramatically slower than the
last time I tested those features. Thinking that I had made a
programming mistake I dug into my code, and while the regexps that I
was using could be tuned for slightly better performance the problem
was not in my code. I then installed textproc/gnugrep to compare,
and the differences were very dramatic using a highly pessimized test
case (finding a match on the last line of INDEX). The script I used
to test is at http://people.freebsd.org/~dougb/grep-time-trial.sh.txt
and a typical result was:
GNU grep
Elapsed time: 2 seconds
BSD grep
Elapsed time: 47 seconds
Ok, I'll take care of this soon, and make GNU grep default, again with
a knob to build BSD grep. I agree with you that we cannot allow such a
big performance drawback but I my measures only showed significant
differences for very big searches and I didn't imagine that it could
add up to such a big diference. I'm sorry for the bad decision I took
making it default.
This should trim some time off BSD grep. It removes the lock/unlock for
each fgetc() by locking/unlocking the file once. stdio can be slow.
You probably want to replace flockfile() with ftrylockfile() if threads
will be involved at some point (threading or making a libgrep that may
be used in a threaded process).
Sean
--
s...@freebsd.org
Index: file.c
===================================================================
--- file.c (revision 210862)
+++ file.c (working copy)
@@ -74,7 +74,7 @@
switch (filebehave) {
case FILE_STDIO:
- return (fgetc(f->f));
+ return (getc_unlocked(f->f));
case FILE_GZIP:
return (gzgetc(f->gzf));
case FILE_BZIP:
@@ -189,6 +189,7 @@
f = grep_malloc(sizeof *f);
if ((f->f = fdopen(STDIN_FILENO, "r")) != NULL) {
+ flockfile(f->f);
f->stdin = true;
return (f);
}
@@ -238,6 +239,7 @@
switch (filebehave) {
case FILE_STDIO:
+ funlockfile(f->f);
fclose(f->f);
break;
case FILE_GZIP:
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