From 9b5f4eb57af28a604cd7ac8b2c1be9e49f0b517d Mon Sep 17 00:00:00 2001
From: Laine Stump <laine@laine.org>
Date: Mon, 28 Sep 2015 17:11:11 -0400
Subject: [PATCH] call aug_load() at most once per second

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1268384

Previously, netcf would call aug_load() at the start of each public
API call, and rely on augeas quickly determining if the files needed
to be reread based on checking the mtime of all files. With a large
number of files (i.e. several hundred ifcfg files) just checking the
mtime of all files ends up taking quite a long time; enough to turn a
simple "virsh iface-list" of 300 bridges + 300 vlans into a 22 second
ordeal.

With this patch applied, netcf will only call aug_load() at most once
every second, resulting in runtime for virsh iface-list going down to
< 1 second.

The trade-off is that the results of a netcf API call could be up to 1
second out of date (but only due to changes in the config external to
netcf). Since ifcfg files change very infrequently, this is likely
acceptable.
---
 src/dutil_linux.c | 8 +++++++-
 src/dutil_linux.h | 1 +
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/dutil_linux.c b/src/dutil_linux.c
index 0850593..24f4d95 100644
--- a/src/dutil_linux.c
+++ b/src/dutil_linux.c
@@ -32,6 +32,7 @@
 #include <unistd.h>
 #include <ctype.h>
 #include <errno.h>
+#include <time.h>
 
 #include <dirent.h>
 #include <sys/wait.h>
@@ -151,6 +152,7 @@ int remove_augeas_xfm_table(struct netcf *ncf,
  */
 augeas *get_augeas(struct netcf *ncf) {
     int r;
+    time_t current_time;
 
     if (ncf->driver->augeas == NULL) {
         augeas *aug;
@@ -186,9 +188,12 @@ augeas *get_augeas(struct netcf *ncf) {
         }
         ncf->driver->copy_augeas_xfm = 0;
         ncf->driver->load_augeas = 1;
+        ncf->driver->load_augeas_time = 0;
     }
 
-    if (ncf->driver->load_augeas) {
+    current_time = time(NULL);
+    if (ncf->driver->load_augeas &&
+        ncf->driver->load_augeas_time != current_time) {
         augeas *aug = ncf->driver->augeas;
 
         r = aug_load(aug);
@@ -207,6 +212,7 @@ augeas *get_augeas(struct netcf *ncf) {
         }
         ERR_THROW(r > 0, ncf, EOTHER, "errors in loading some config files");
         ncf->driver->load_augeas = 0;
+        ncf->driver->load_augeas_time = current_time;
     }
     return ncf->driver->augeas;
  error:
diff --git a/src/dutil_linux.h b/src/dutil_linux.h
index a06a15c..75ac631 100644
--- a/src/dutil_linux.h
+++ b/src/dutil_linux.h
@@ -41,6 +41,7 @@ struct driver {
     struct nl_sock     *nl_sock;
     struct nl_cache   *link_cache;
     struct nl_cache   *addr_cache;
+    time_t             load_augeas_time;
     unsigned int       load_augeas : 1;
     unsigned int       copy_augeas_xfm : 1;
     unsigned int       augeas_xfm_num_tables;
-- 
2.4.3