So I tinkered with the way ksh(1) tracks memory allocation, trying to
make it faster in the general case. One approach used a RB tree,
I wrote since a simple hash table implementation which seems to work
rather well.
But the actual problem I'd first like to solve is a corner case. I use
HISTSIZE=20000, and when the actual line count in my histfile approaches
25000 (1.25 * HISTSIZE), ksh(1) has a hard time handling it. The main
reason is that it calls afree() ~5000 times in a loop, with afree()
traversing the APERM freelist, which contains >20000 elements. This is
expensive.
For history lines, we don't actually need to keep track of allocations
using an area, history lines are private to history.c and no gc/whatever
is needed there. So here's a diff that just uses strdup(3)/free(3).
Comments? ok?
Index: history.c
===================================================================
RCS file: /d/cvs/src/bin/ksh/history.c,v
retrieving revision 1.64
diff -u -p -p -u -r1.64 history.c
--- history.c 11 Aug 2017 19:37:58 -0000 1.64
+++ history.c 15 Aug 2017 01:14:58 -0000
@@ -428,7 +428,7 @@ histbackup(void)
if (histptr >= history && last_line != hist_source->line) {
hist_source->line--;
- afree(*histptr, APERM);
+ free(*histptr);
histptr--;
last_line = hist_source->line;
}
@@ -613,14 +613,15 @@ histsave(int lno, const char *cmd, int d
#endif
}
- c = str_save(cmd, APERM);
+ if ((c = strdup(cmd)) == NULL)
+ internal_errorf(1, "unable to allocate memory");
if ((cp = strrchr(c, '\n')) != NULL)
*cp = '\0';
if (histptr < history + histsize - 1)
histptr++;
else { /* remove oldest command */
- afree(*history, APERM);
+ free(*history);
memmove(history, history + 1,
(histsize - 1) * sizeof(*history));
}
--
jca | PGP : 0x1524E7EE / 5135 92C1 AD36 5293 2BDF DDCC 0DFA 74AE 1524 E7EE
