Re: getaddrinfo performance

Bill Stoddard wrote:

>I'm doing some profiling of mod_proxy configured as a gateway (aka reverse
>proxy) on AIX. Over 50% of the cycles to handle a request are chewed up in
>getaddrinfo() (getaddrinfo is doing memsets on big chunks of storage among
>other things).
>
the other thing you could look at is caching the results ..
for reverse proxy calls you usually only look at a 5-10 host names and 
you could cache the dns respones
for them. This would work extermly well is you have the backend boxes 
all behind a single IP

>
>Here is the call in ap_proxy_http_determine_connection() that wrappers
>getaddrinfo.
>
>err = apr_sockaddr_info_get(&uri_addr, apr_pstrdup(c->pool, uri->hostname),
>                                APR_UNSPEC, uri->port, 0, c->pool);
>
>
>Changing APR_UNSPEC to APR_INET nearly doubles the throughput (140 rps to
>265 rps). Replacing getaddrinfo with gethostbyname_r will get the benchmark
>to 280 rps. Allan Edwards is reporting significant performance hit on
>Windows as well (though not as severe as I'm seeing on AIX).  Looks like we
>may need a config directive to tell the server to use AF_INET or AF_INETV6.
>
>Bill
>  
>