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authorUlrich Drepper <drepper@gmail.com>2012-03-30 07:42:29 -0400
committerUlrich Drepper <drepper@gmail.com>2012-03-30 07:42:29 -0400
commitc030f70c8796c7743c3aa97d6beff3bd5b8dcd5d (patch)
treef0cf2dae6b9d0b0f7f36ddc89965d138fb9c6ffc /resolv
parent1d39e35923d086a0248f1934adfe31d8f6c813c0 (diff)
downloadglibc-c030f70c8796c7743c3aa97d6beff3bd5b8dcd5d.tar.gz
Speed up DNS by avoiding a system call if possible
Diffstat (limited to 'resolv')
-rw-r--r--resolv/res_send.c100
1 files changed, 83 insertions, 17 deletions
diff --git a/resolv/res_send.c b/resolv/res_send.c
index a001c1e753..0b5bc91995 100644
--- a/resolv/res_send.c
+++ b/resolv/res_send.c
@@ -1013,8 +1013,9 @@ send_dg(res_state statp,
seconds /= statp->nscount;
if (seconds <= 0)
seconds = 1;
- bool single_request = (statp->options & RES_SNGLKUP) != 0;
bool single_request_reopen = (statp->options & RES_SNGLKUPREOP) != 0;
+ bool single_request = (((statp->options & RES_SNGLKUP) != 0)
+ | single_request_reopen);
int save_gotsomewhere = *gotsomewhere;
int retval;
@@ -1100,24 +1101,89 @@ send_dg(res_state statp,
}
__set_errno (0);
if (pfd[0].revents & POLLOUT) {
- ssize_t sr;
- if (nwritten != 0)
- sr = send (pfd[0].fd, buf2, buflen2, MSG_NOSIGNAL);
- else
- sr = send (pfd[0].fd, buf, buflen, MSG_NOSIGNAL);
+#ifndef __ASSUME_SENDMMSG
+ static int have_sendmmsg;
+#else
+# define have_sendmmsg 1
+#endif
+ if (have_sendmmsg >= 0 && nwritten == 0 && buf2 != NULL
+ && !single_request)
+ {
+ struct iovec iov[2];
+ struct mmsghdr reqs[2];
+ reqs[0].msg_hdr.msg_name = NULL;
+ reqs[0].msg_hdr.msg_namelen = 0;
+ reqs[0].msg_hdr.msg_iov = &iov[0];
+ reqs[0].msg_hdr.msg_iovlen = 1;
+ iov[0].iov_base = (void *) buf;
+ iov[0].iov_len = buflen;
+ reqs[0].msg_hdr.msg_control = NULL;
+ reqs[0].msg_hdr.msg_controllen = 0;
+
+ reqs[1].msg_hdr.msg_name = NULL;
+ reqs[1].msg_hdr.msg_namelen = 0;
+ reqs[1].msg_hdr.msg_iov = &iov[1];
+ reqs[1].msg_hdr.msg_iovlen = 1;
+ iov[1].iov_base = (void *) buf2;
+ iov[1].iov_len = buflen2;
+ reqs[1].msg_hdr.msg_control = NULL;
+ reqs[1].msg_hdr.msg_controllen = 0;
+
+ int ndg = sendmmsg (pfd[0].fd, reqs, 2, MSG_NOSIGNAL);
+ if (__builtin_expect (ndg == 2, 1))
+ {
+ assert (reqs[0].msg_len == buflen);
+ assert (reqs[1].msg_len == buflen2);
- if (sr != buflen) {
- if (errno == EINTR || errno == EAGAIN)
- goto recompute_resend;
- Perror(statp, stderr, "send", errno);
+ pfd[0].events = POLLIN;
+ nwritten += 2;
+ }
+ else if (ndg == 1 && reqs[0].msg_len == buflen)
+ goto just_one;
+ else if (errno == EINTR || errno == EAGAIN)
+ goto recompute_resend;
+ else
+ {
+#ifndef __ASSUME_SENDMMSG
+ if (have_sendmmsg == 0)
+ {
+ if (errno == ENOSYS)
+ {
+ have_sendmmsg = -1;
+ goto try_send;
+ }
+ have_sendmmsg = 1;
+ }
+#endif
+
+ Perror(statp, stderr, "sendmmsg", errno);
goto err_out;
- }
- if (nwritten != 0 || buf2 == NULL
- || single_request || single_request_reopen)
- pfd[0].events = POLLIN;
+ }
+ }
else
- pfd[0].events = POLLIN | POLLOUT;
- ++nwritten;
+ {
+ ssize_t sr;
+#ifndef __ASSUME_SENDMMSG
+ try_send:
+#endif
+ if (nwritten != 0)
+ sr = send (pfd[0].fd, buf2, buflen2, MSG_NOSIGNAL);
+ else
+ sr = send (pfd[0].fd, buf, buflen, MSG_NOSIGNAL);
+
+ if (sr != buflen) {
+ if (errno == EINTR || errno == EAGAIN)
+ goto recompute_resend;
+ Perror(statp, stderr, "send", errno);
+ goto err_out;
+ }
+ just_one:
+ if (nwritten != 0 || buf2 == NULL || single_request)
+ pfd[0].events = POLLIN;
+ else
+ pfd[0].events = POLLIN | POLLOUT;
+ ++nwritten;
+ }
goto wait;
} else if (pfd[0].revents & POLLIN) {
int *thisanssizp;
@@ -1327,7 +1393,7 @@ send_dg(res_state statp,
recvresp2 = 1;
/* Repeat waiting if we have a second answer to arrive. */
if ((recvresp1 & recvresp2) == 0) {
- if (single_request || single_request_reopen) {
+ if (single_request) {
pfd[0].events = POLLOUT;
if (single_request_reopen) {
__res_iclose (statp, false);