The patch titled
Subject: fixdep: faster CONFIG_ search
has been added to the -mm tree. Its filename is
fixdep-faster-config_-search.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/fixdep-faster-config_-search.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/fixdep-faster-config_-search.patch
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------------------------------------------------------
From: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Subject: fixdep: faster CONFIG_ search
Do you think kernel build is 100% dominated by gcc? You are wrong! One
small utility called "fixdep" consistently manages to sneak into profile's
first page (unless you have small monitor of course).
The choke point is this clever code:
for (; m < end; m++) {
if (*m == INT_CONF) { p = (char *) m ; goto conf; }
if (*m == INT_ONFI) { p = (char *) m-1; goto conf; }
if (*m == INT_NFIG) { p = (char *) m-2; goto conf; }
if (*m == INT_FIG_) { p = (char *) m-3; goto conf; }
4 branches per 4 characters is not fast.
Use strstr(3), so that SSE2 etc can be used.
With this patch, fixdep is so deep at the bottom, it is hard to find it.
Link: http://lkml.kernel.org/r/20160823184724.GA11707@xxxxxxxxxxxxxxx
Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Cc: Michal Marek <mmarek@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
scripts/basic/fixdep.c | 67 ++++++++++++++++-----------------------
1 file changed, 28 insertions(+), 39 deletions(-)
diff -puN scripts/basic/fixdep.c~fixdep-faster-config_-search scripts/basic/fixdep.c
--- a/scripts/basic/fixdep.c~fixdep-faster-config_-search
+++ a/scripts/basic/fixdep.c
@@ -82,8 +82,7 @@
* to date before even starting the recursive build, so it's too late
* at this point anyway.
*
- * The algorithm to grep for "CONFIG_..." is bit unusual, but should
- * be fast ;-) We don't even try to really parse the header files, but
+ * We don't even try to really parse the header files, but
* merely grep, i.e. if CONFIG_FOO is mentioned in a comment, it will
* be picked up as well. It's not a problem with respect to
* correctness, since that can only give too many dependencies, thus
@@ -241,37 +240,22 @@ static void use_config(const char *m, in
print_config(m, slen);
}
-static void parse_config_file(const char *map, size_t len)
+static void parse_config_file(const char *p)
{
- const int *end = (const int *) (map + len);
- /* start at +1, so that p can never be < map */
- const int *m = (const int *) map + 1;
- const char *p, *q;
-
- for (; m < end; m++) {
- if (*m == INT_CONF) { p = (char *) m ; goto conf; }
- if (*m == INT_ONFI) { p = (char *) m-1; goto conf; }
- if (*m == INT_NFIG) { p = (char *) m-2; goto conf; }
- if (*m == INT_FIG_) { p = (char *) m-3; goto conf; }
- continue;
- conf:
- if (p > map + len - 7)
- continue;
- if (memcmp(p, "CONFIG_", 7))
- continue;
- p += 7;
- for (q = p; q < map + len; q++) {
- if (!(isalnum(*q) || *q == '_'))
- goto found;
- }
- continue;
+ const char *q, *r;
- found:
- if (!memcmp(q - 7, "_MODULE", 7))
- q -= 7;
- if (q - p < 0)
- continue;
- use_config(p, q - p);
+ while ((p = strstr(p, "CONFIG_"))) {
+ p += 7;
+ q = p;
+ while (*q && (isalnum(*q) || *q == '_'))
+ q++;
+ if (memcmp(q - 7, "_MODULE", 7) == 0)
+ r = q - 7;
+ else
+ r = q;
+ if (r > p)
+ use_config(p, r - p);
+ p = q;
}
}
@@ -291,7 +275,7 @@ static void do_config_file(const char *f
{
struct stat st;
int fd;
- void *map;
+ char *map;
fd = open(filename, O_RDONLY);
if (fd < 0) {
@@ -308,18 +292,23 @@ static void do_config_file(const char *f
close(fd);
return;
}
- map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
- if ((long) map == -1) {
- perror("fixdep: mmap");
+ map = malloc(st.st_size + 1);
+ if (!map) {
+ perror("fixdep: malloc");
close(fd);
return;
}
+ if (read(fd, map, st.st_size) != st.st_size) {
+ perror("fixdep: read");
+ close(fd);
+ return;
+ }
+ map[st.st_size] = '\0';
+ close(fd);
- parse_config_file(map, st.st_size);
-
- munmap(map, st.st_size);
+ parse_config_file(map);
- close(fd);
+ free(map);
}
/*
_
Patches currently in -mm which might be from adobriyan@xxxxxxxxx are
kbuild-simpler-generation-of-assembly-constants.patch
fixdep-faster-config_-search.patch
mm-unrig-vma-cache-hit-ratio.patch
proc-much-faster-proc-vmstat.patch
proc-faster-proc-status.patch
cred-simpler-1d-supplementary-groups.patch
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