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Use open address hashtable with multiplicative double hash probing 

and exponential hashtable growth for tracking previously seen inodes.
This replaces the O(n^2) behavior of linkchk() with an implementation
that should be O(n*logn)
This addresses NetBSD PR bin/25857
This commit is contained in:
dbj 2004-06-13 11:30:10 +00:00
parent 64c877a4e9
commit 44b22e2058
1 changed files with 75 additions and 30 deletions
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105
usr.bin/du/du.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: du.c,v 1.24 2004/05/17 01:56:19 simonb Exp $ */
/* $NetBSD: du.c,v 1.25 2004/06/13 11:30:10 dbj Exp $ */
/*
* Copyright (c) 1989, 1993, 1994
@ -42,7 +42,7 @@ __COPYRIGHT("@(#) Copyright (c) 1989, 1993, 1994\n\
#if 0
static char sccsid[] = "@(#)du.c 8.5 (Berkeley) 5/4/95";
#else
__RCSID("$NetBSD: du.c,v 1.24 2004/05/17 01:56:19 simonb Exp $");
__RCSID("$NetBSD: du.c,v 1.25 2004/06/13 11:30:10 dbj Exp $");
#endif
#endif /* not lint */
@ -58,8 +58,9 @@ __RCSID("$NetBSD: du.c,v 1.24 2004/05/17 01:56:19 simonb Exp $");
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <limits.h>
int linkchk __P((FTSENT *));
int linkchk __P((dev_t, ino_t));
int main __P((int, char **));
void prstat __P((const char *, int64_t));
void usage __P((void));
@ -217,7 +218,8 @@ main(argc, argv)
rval = 1;
break;
default:
if (p->fts_statp->st_nlink > 1 && linkchk(p))
if (p->fts_statp->st_nlink > 1 &&
linkchk(p->fts_statp->st_dev, p->fts_statp->st_ino))
break;
/*
* If listing each file, or a non-directory file was
@ -254,36 +256,79 @@ prstat(const char *fname, int64_t blocks)
fname);
}
typedef struct _ID {
dev_t dev;
ino_t inode;
} ID;
int
linkchk(p)
FTSENT *p;
linkchk(dev_t dev, ino_t ino)
{
static ID *files;
static int maxfiles, nfiles;
ID *fp, *start;
ino_t ino;
dev_t dev;
static struct entry {
dev_t dev;
ino_t ino;
} *htable;
static int htshift; /* log(allocated size) */
static int htmask; /* allocated size - 1 */
static int htused; /* 2*number of insertions */
static int sawzero; /* Whether zero is in table or not */
int h, h2;
uint64_t tmp;
/* this constant is (1<<64)/((1+sqrt(5))/2)
* aka (word size)/(golden ratio)
*/
const uint64_t HTCONST = 11400714819323198485ULL;
const int HTBITS = CHAR_BIT * sizeof(tmp);
ino = p->fts_statp->st_ino;
dev = p->fts_statp->st_dev;
if ((start = files) != NULL)
for (fp = start + nfiles - 1; fp >= start; --fp)
if (ino == fp->inode && dev == fp->dev)
return (1);
/* Never store zero in hashtable */
if (dev == 0 && ino == 0) {
h = sawzero;
sawzero = 1;
return h;
}
if (nfiles == maxfiles && (files = realloc((char *)files,
(u_int)(sizeof(ID) * (maxfiles += 128)))) == NULL)
err(1, "realloc");
files[nfiles].inode = ino;
files[nfiles].dev = dev;
++nfiles;
return (0);
/* Extend hash table if necessary, keep load under 0.5 */
if (htused<<1 >= htmask) {
struct entry *ohtable;
if (!htable)
htshift = 10; /* starting hashtable size */
else
htshift++; /* exponential hashtable growth */
htmask = (1 << htshift) - 1;
htused = 0;
ohtable = htable;
htable = calloc(htmask+1, sizeof(*htable));
if (!htable)
err(1, "calloc");
/* populate newly allocated hashtable */
if (ohtable) {
int i;
for (i = 0; i <= htmask>>1; i++)
if (ohtable[i].ino || ohtable[i].dev)
linkchk(ohtable[i].dev, ohtable[i].ino);
free(ohtable);
}
}
/* multiplicative hashing */
tmp = dev;
tmp <<= HTBITS>>1;
tmp |= ino;
tmp *= HTCONST;
h = tmp >> (HTBITS - htshift);
h2 = 1 | ( tmp >> (HTBITS - (htshift<<1) - 1)); /* must be odd */
/* open address hashtable search with double hash probing */
while (htable[h].ino || htable[h].dev) {
if ((htable[h].ino == ino) && (htable[h].dev == dev))
return 1;
h = (h + h2) & htmask;
}
/* Insert the current entry into hashtable */
htable[h].dev = dev;
htable[h].ino = ino;
htused++;
return 0;
}
void