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author | Eric Dumazet <eric.dumazet@gmail.com> | 2010-11-09 16:29:27 +0100 |
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committer | Michal Marek <mmarek@suse.cz> | 2010-11-11 17:12:06 +0100 |
commit | 8af27e1dc4e4dd7a7b04c2cd0fc3d419d91d45b0 (patch) | |
tree | 0cf6febb82aafa421259a69007a6e848c3b9fa3c /scripts | |
parent | initramfs: Fix build break on symbol-prefixed archs (diff) | |
download | linux-8af27e1dc4e4dd7a7b04c2cd0fc3d419d91d45b0.tar.xz linux-8af27e1dc4e4dd7a7b04c2cd0fc3d419d91d45b0.zip |
fixdep: use hash table instead of a single array
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>
Diffstat (limited to 'scripts')
-rw-r--r-- | scripts/basic/fixdep.c | 109 |
1 files changed, 61 insertions, 48 deletions
diff --git a/scripts/basic/fixdep.c b/scripts/basic/fixdep.c index ea26b23de082..ed0584623690 100644 --- a/scripts/basic/fixdep.c +++ b/scripts/basic/fixdep.c @@ -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) -{ - 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); } - } -} +#define HASHSZ 256 +static struct item *hashtab[HASHSZ]; +static unsigned int strhash(const char *str, unsigned int sz) +{ + /* 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); - - memcpy(s, m, slen); s[slen] = 0; + define_config(m, slen, hash); - 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; |