* nscd/nscd_getgr_r.c (nscd_getgr_r): Optimize a bit: use simpler

	read mechanism when there are no group members and avoid no-op
	read syscall in this case.

diff --git a/ChangeLog b/ChangeLog
index b0400a1..13bf1dc 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2007-10-13  Ulrich Drepper  <drepper@redhat.com>
 
+       * nscd/nscd_getgr_r.c (nscd_getgr_r): Optimize a bit: use simpler
+       read mechanism when there are no group members and avoid no-op
+       read syscall in this case.
+
        [BZ #3242]
        * nscd/nscd_helper.c (wait_on_socket): Take timeout as parameter.
        (__readall): If reading failed due to EAGAIN error wait a bit

diff --git a/nscd/nscd_getgr_r.c b/nscd/nscd_getgr_r.c
index fc036f2..543ee17 100644 (file)
--- a/nscd/nscd_getgr_r.c
+++ b/nscd/nscd_getgr_r.c
@@ -190,26 +190,37 @@ nscd_getgr_r (const char *key, size_t keylen, request_type type,
       /* Read the length information, group name, and password.  */
       if (gr_name == NULL)
        {
-         /* Allocate array to store lengths.  */
-         if (lensize == 0)
+         /* Handle a simple, usual case: no group members.  */
+         if (__builtin_expect (gr_resp.gr_mem_cnt == 0, 1))
            {
-             lensize = gr_resp.gr_mem_cnt * sizeof (uint32_t);
-             len = (uint32_t *) alloca (lensize);
+             size_t n = gr_resp.gr_name_len + gr_resp.gr_passwd_len;
+             if (__builtin_expect (__readall (sock, resultbuf->gr_name, n)
+                                   != (ssize_t) n, 0))
+               goto out_close;
+           }
+         else
+           {
+             /* Allocate array to store lengths.  */
+             if (lensize == 0)
+               {
+                 lensize = gr_resp.gr_mem_cnt * sizeof (uint32_t);
+                 len = (uint32_t *) alloca (lensize);
+               }
+             else if (gr_resp.gr_mem_cnt * sizeof (uint32_t) > lensize)
+               len = extend_alloca (len, lensize,
+                                    gr_resp.gr_mem_cnt * sizeof (uint32_t));
+
+             vec[0].iov_base = (void *) len;
+             vec[0].iov_len = gr_resp.gr_mem_cnt * sizeof (uint32_t);
+             vec[1].iov_base = resultbuf->gr_name;
+             vec[1].iov_len = gr_resp.gr_name_len + gr_resp.gr_passwd_len;
+             total_len = vec[0].iov_len + vec[1].iov_len;
+
+             /* Get this data.  */
+             size_t n = __readvall (sock, vec, 2);
+             if (__builtin_expect (n != total_len, 0))
+               goto out_close;
            }
-         else if (gr_resp.gr_mem_cnt * sizeof (uint32_t) > lensize)
-           len = extend_alloca (len, lensize,
-                                gr_resp.gr_mem_cnt * sizeof (uint32_t));
-
-         vec[0].iov_base = (void *) len;
-         vec[0].iov_len = gr_resp.gr_mem_cnt * sizeof (uint32_t);
-         vec[1].iov_base = resultbuf->gr_name;
-         vec[1].iov_len = gr_resp.gr_name_len + gr_resp.gr_passwd_len;
-         total_len = vec[0].iov_len + vec[1].iov_len;
-
-         /* Get this data.  */
-         size_t n = __readvall (sock, vec, 2);
-         if (__builtin_expect (n != total_len, 0))
-           goto out_close;
        }
       else
        /* We already have the data.  Just copy the group name and
@@ -251,37 +262,42 @@ nscd_getgr_r (const char *key, size_t keylen, request_type type,
        }
 
       retval = 0;
-      if (gr_name == NULL)
+
+      /* If there are no group members TOTAL_LEN is zero.  */
+      if (total_len > 0)
        {
-         size_t n = __readall (sock, resultbuf->gr_mem[0], total_len);
-         if (__builtin_expect (n != total_len, 0))
+         if (gr_name == NULL)
            {
-             /* The `errno' to some value != ERANGE.  */
-             __set_errno (ENOENT);
-             retval = ENOENT;
+             size_t n = __readall (sock, resultbuf->gr_mem[0], total_len);
+             if (__builtin_expect (n != total_len, 0))
+               {
+                 /* The `errno' to some value != ERANGE.  */
+                 __set_errno (ENOENT);
+                 retval = ENOENT;
+               }
+             else
+               *result = resultbuf;
            }
          else
-           *result = resultbuf;
-       }
-      else
-       {
-         /* Copy the group member names.  */
-         memcpy (resultbuf->gr_mem[0], gr_name + gr_name_len, total_len);
-
-         /* Try to detect corrupt databases.  */
-         if (resultbuf->gr_name[gr_name_len - 1] != '\0'
-             || resultbuf->gr_passwd[gr_resp.gr_passwd_len - 1] != '\0'
-             || ({for (cnt = 0; cnt < gr_resp.gr_mem_cnt; ++cnt)
-                    if (resultbuf->gr_mem[cnt][len[cnt] - 1] != '\0')
-                      break;
-                  cnt < gr_resp.gr_mem_cnt; }))
            {
-             /* We cannot use the database.  */
-             retval = mapped->head->gc_cycle != gc_cycle ? -2 : -1;
-             goto out_close;
+             /* Copy the group member names.  */
+             memcpy (resultbuf->gr_mem[0], gr_name + gr_name_len, total_len);
+
+             /* Try to detect corrupt databases.  */
+             if (resultbuf->gr_name[gr_name_len - 1] != '\0'
+                 || resultbuf->gr_passwd[gr_resp.gr_passwd_len - 1] != '\0'
+                 || ({for (cnt = 0; cnt < gr_resp.gr_mem_cnt; ++cnt)
+                       if (resultbuf->gr_mem[cnt][len[cnt] - 1] != '\0')
+                         break;
+                     cnt < gr_resp.gr_mem_cnt; }))
+               {
+                 /* We cannot use the database.  */
+                 retval = mapped->head->gc_cycle != gc_cycle ? -2 : -1;
+                 goto out_close;
+               }
+
+             *result = resultbuf;
            }
-
-         *result = resultbuf;
        }
     }
   else