Hello!
I found out that getaddrinfo() function in uclibc may cause performance
downgrades for some heavy-loaded services (e.g. squid) due to
unnecessary calls to __check_pf() (and hence getifaddrs() ). Really
these calls only needed when AI_ADDRCONFIG hint flag is given.
For example, squid uses getaddrinfo() to convert IP addresses from
textual to numeric form, providing just AI_NUMERICHOST hint flag. You
can imagine how many calls there are when you have about 1000 requests
per second and the overhead from netlink communications to kernel every
time in getifaddrs().
Small simple patch to fix this issue is attached.
--
Best wishes,
Alexander Komyagin
--- git.orig/libc/inet/getaddrinfo.c 2012-03-29 18:32:08.487911701 +0400
+++ git/libc/inet/getaddrinfo.c 2012-03-29 18:32:25.735299532 +0400
@@ -401,7 +401,14 @@
int rc;
int v4mapped = (req->ai_family == PF_UNSPEC || req->ai_family == PF_INET6)
&& (req->ai_flags & AI_V4MAPPED);
- unsigned seen = __check_pf();
+
+ //"seen" variable won't be used if AI_ADDRCONFIG is
+ // not specified. So avoid unnecessary call to __check_pf()
+ // since it can be costly esp. when RSBAC-Net is enabled.
+ unsigned seen = 0;
+ if (req->ai_flags & AI_ADDRCONFIG) {
+ seen = __check_pf();
+ }
memset(&nullserv, 0, sizeof(nullserv));
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