git: 0477149e585f - stable/13 - Optimize res_find().

[Alexander Motin]

The branch stable/13 has been updated by mav:

URL: https://cgit.FreeBSD.org/src/commit/?id=0477149e585f142ca9e6732d198da470a0c346f3

commit 0477149e585f142ca9e6732d198da470a0c346f3
Author:     Alexander Motin <mav at FreeBSD.org>
AuthorDate: 2021-08-09 01:34:33 +0000
Commit:     Alexander Motin <mav at FreeBSD.org>
CommitDate: 2021-08-23 01:15:47 +0000

    Optimize res_find().
    
    When the device name is provided, we can simply run strncmp() for each
    line to quickly skip unrelated ones, that is much faster than sscanf()
    and only then strcmp().
    
    MFC after:      2 weeks
    
    (cherry picked from commit 696fca3fd491972e615195f2ce94598b9c469cac)
---
 sys/kern/subr_hints.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/sys/kern/subr_hints.c b/sys/kern/subr_hints.c
index 3614659ebcf2..b16761d7d6fc 100644
--- a/sys/kern/subr_hints.c
+++ b/sys/kern/subr_hints.c
@@ -127,7 +127,7 @@ res_find(char **hintp_cookie, int *line, int *startln,
     const char **ret_name, int *ret_namelen, int *ret_unit,
     const char **ret_resname, int *ret_resnamelen, const char **ret_value)
 {
-	int fbacklvl = FBACK_MDENV, i = 0, n = 0;
+	int fbacklvl = FBACK_MDENV, i = 0, n = 0, namelen;
 	char r_name[32];
 	int r_unit;
 	char r_resname[32];
@@ -229,12 +229,16 @@ fallback:
 		i = 0;
 	}
 
+	if (name)
+		namelen = strlen(name);
 	cp = hintp;
 	while (cp) {
 		(*line)++;
 		if (strncmp(cp, "hint.", 5) != 0)
 			goto nexthint;
-		n = sscanf(cp, "hint.%32[^.].%d.%32[^=]=%127s", r_name, &r_unit,
+		if (name && strncmp(cp + 5, name, namelen) != 0)
+			goto nexthint;
+		n = sscanf(cp + 5, "%32[^.].%d.%32[^=]=%127s", r_name, &r_unit,
 		    r_resname, r_value);
 		if (n != 4) {
 			printf("CONFIG: invalid hint '%s'\n", cp);