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fixdep: use hash table instead of a single array

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I noticed fixdep uses ~2% of cpu time in kernel build, in function
use_config()

fixdep spends a lot of cpu cycles in linear searches in its internal
string array. With about 400 stored strings per dep file, this begins to
be noticeable.

Convert fixdep to use a hash table.

kbuild results on my x86_64 allmodconfig

Before patch :

real	10m30.414s
user	61m51.456s
sys	8m28.200s

real	10m12.334s
user	61m50.236s
sys	8m30.448s

real	10m42.947s
user	61m50.028s
sys	8m32.380s

After:

real	10m8.180s
user	61m22.506s
sys	8m32.384s

real	10m35.039s
user	61m21.654s
sys	8m32.212s

real	10m14.487s
user	61m23.498s
sys	8m32.312s

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>
This commit is contained in:
Eric Dumazet 2010-11-09 16:29:27 +01:00 committed by Michal Marek
parent d63f6d1b4d
commit 8af27e1dc4
1 changed files with 61 additions and 48 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

109
scripts/basic/fixdep.c
View file

@ -138,38 +138,36 @@ static void print_cmdline(void)
printf("cmd_%s := %s\n\n", target, cmdline);
}
char * str_config = NULL;
int size_config = 0;
int len_config = 0;
struct item {
struct item *next;
unsigned int len;
unsigned int hash;
char name[0];
};
/*
* Grow the configuration string to a desired length.
* Usually the first growth is plenty.
*/
static void grow_config(int len)
#define HASHSZ 256
static struct item *hashtab[HASHSZ];
static unsigned int strhash(const char *str, unsigned int sz)
{
while (len_config + len > size_config) {
if (size_config == 0)
size_config = 2048;
str_config = realloc(str_config, size_config *= 2);
if (str_config == NULL)
{ perror("fixdep:malloc"); exit(1); }
}
/* fnv32 hash */
unsigned int i, hash = 2166136261U;
for (i = 0; i < sz; i++)
hash = (hash ^ str[i]) * 0x01000193;
return hash;
}
/*
* Lookup a value in the configuration string.
*/
static int is_defined_config(const char * name, int len)
static int is_defined_config(const char *name, int len, unsigned int hash)
{
const char * pconfig;
const char * plast = str_config + len_config - len;
for ( pconfig = str_config + 1; pconfig < plast; pconfig++ ) {
if (pconfig[ -1] == '\n'
&& pconfig[len] == '\n'
&& !memcmp(pconfig, name, len))
struct item *aux;
for (aux = hashtab[hash % HASHSZ]; aux; aux = aux->next) {
if (aux->hash == hash && aux->len == len &&
memcmp(aux->name, name, len) == 0)
return 1;
}
return 0;
@ -178,13 +176,19 @@ static int is_defined_config(const char * name, int len)
/*
* Add a new value to the configuration string.
*/
static void define_config(const char * name, int len)
static void define_config(const char *name, int len, unsigned int hash)
{
grow_config(len + 1);
struct item *aux = malloc(sizeof(*aux) + len);
memcpy(str_config+len_config, name, len);
len_config += len;
str_config[len_config++] = '\n';
if (!aux) {
perror("fixdep:malloc");
exit(1);
}
memcpy(aux->name, name, len);
aux->len = len;
aux->hash = hash;
aux->next = hashtab[hash % HASHSZ];
hashtab[hash % HASHSZ] = aux;
}
/*
@ -192,40 +196,49 @@ static void define_config(const char * name, int len)
*/
static void clear_config(void)
{
len_config = 0;
define_config("", 0);
struct item *aux, *next;
unsigned int i;
for (i = 0; i < HASHSZ; i++) {
for (aux = hashtab[i]; aux; aux = next) {
next = aux->next;
free(aux);
}
hashtab[i] = NULL;
}
}
/*
* Record the use of a CONFIG_* word.
*/
static void use_config(char *m, int slen)
static void use_config(const char *m, int slen)
{
char s[PATH_MAX];
char *p;
unsigned int hash = strhash(m, slen);
int c, i;
if (is_defined_config(m, slen))
if (is_defined_config(m, slen, hash))
return;
define_config(m, slen);
define_config(m, slen, hash);
memcpy(s, m, slen); s[slen] = 0;
for (p = s; p < s + slen; p++) {
if (*p == '_')
*p = '/';
printf(" $(wildcard include/config/");
for (i = 0; i < slen; i++) {
c = m[i];
if (c == '_')
c = '/';
else
*p = tolower((int)*p);
c = tolower(c);
putchar(c);
}
printf(" $(wildcard include/config/%s.h) \\\n", s);
printf(".h) \\\n");
}
static void parse_config_file(char *map, size_t len)
static void parse_config_file(const char *map, size_t len)
{
int *end = (int *) (map + len);
const int *end = (const int *) (map + len);
/* start at +1, so that p can never be < map */
int *m = (int *) map + 1;
char *p, *q;
const int *m = (const int *) map + 1;
const char *p, *q;
for (; m < end; m++) {
if (*m == INT_CONF) { p = (char *) m ; goto conf; }
@ -265,7 +278,7 @@ static int strrcmp(char *s, char *sub)
return memcmp(s + slen - sublen, sub, sublen);
}
static void do_config_file(char *filename)
static void do_config_file(const char *filename)
{
struct stat st;
int fd;