[PATCH iproute2-next v2 0/3] Improve batch and dump times by caching link lookups

[PATCH iproute2-next v2 0/3] Improve batch and dump times by caching link lookups

[David Ahern]

From: David Ahern <dsahern@gmail.com>

Many commands convert device names to an index using ll_name_to_index and
the reverse from an index to a name using ll_index_to_name.

At the moment both of the ll_ functions use the ioctl based helpers from
glibc which involves opening socket, calling ioctl and then closing the
socket on each device lookup. When using a batch file or dumping large
number of routes this means the same device lookups can be done repeatedly
adding unnecessary overhead to both operations.

This series adds a new function, ll_link_get, to send a netlink based
RTM_GETLINK. If successful, the result is cached in idx_head and name_head
so future lookups can re-use the entry. iproute2's ll_map functions are
updated to use ll_link_get over the glibc functions. The result is a
significant speed up in both batch and dumps with negligible overhead if
ip is invoked for single operations.

The first 2 patches add a means to drop an entry from the cache and updates
iplink_modify to use that new function to drop entries on device changes.
This forces the cache to re-learn device information if a batch file has a
mix of link set operations with other commands - such as adding a route.

v2
- changed the second patch to drop cache entry on any link changes
- added ll_link_get to index to name conversion improving dumps

David Ahern (3):
  ll_map: Add function to remove link cache entry by index
  ip link: Drop cache entry on any changes
  Improve batch and dump times by caching link lookups

 include/ll_map.h |  1 +
 ip/iplink.c      |  3 +++
 lib/ll_map.c     | 66 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 69 insertions(+), 1 deletion(-)

-- 
2.11.0

[PATCH iproute2-next v2 1/3] ll_map: Add function to remove link cache entry by index

[David Ahern]

From: David Ahern <dsahern@gmail.com>

Add ll_drop_by_index to remove an entry from the link cache.

Signed-off-by: David Ahern <dsahern@gmail.com>
---
 include/ll_map.h |  1 +
 lib/ll_map.c     | 14 ++++++++++++++
 2 files changed, 15 insertions(+)

diff --git a/include/ll_map.h b/include/ll_map.h
index 511fe00b8567..4de1041e2746 100644
--- a/include/ll_map.h
+++ b/include/ll_map.h
@@ -9,6 +9,7 @@ unsigned ll_name_to_index(const char *name);
 const char *ll_index_to_name(unsigned idx);
 int ll_index_to_type(unsigned idx);
 int ll_index_to_flags(unsigned idx);
+void ll_drop_by_index(unsigned index);
 unsigned namehash(const char *str);
 
 const char *ll_idx_n2a(unsigned int idx);
diff --git a/lib/ll_map.c b/lib/ll_map.c
index 1ab8ef0758ac..8e8a0b1e9c9d 100644
--- a/lib/ll_map.c
+++ b/lib/ll_map.c
@@ -210,6 +210,20 @@ unsigned ll_name_to_index(const char *name)
 	return idx;
 }
 
+void ll_drop_by_index(unsigned index)
+{
+	struct ll_cache *im;
+
+	im = ll_get_by_index(index);
+	if (!im)
+		return;
+
+	hlist_del(&im->idx_hash);
+	hlist_del(&im->name_hash);
+
+	free(im);
+}
+
 void ll_init_map(struct rtnl_handle *rth)
 {
 	static int initialized;
-- 
2.11.0

[PATCH iproute2-next v2 2/3] ip link: Drop cache entry on any changes

[David Ahern]

From: David Ahern <dsahern@gmail.com>

Remove any entry from the link cache when the link is modified.

Signed-off-by: David Ahern <dsahern@gmail.com>
---
 ip/iplink.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/ip/iplink.c b/ip/iplink.c
index b5519201fef7..393cefdc89df 100644
--- a/ip/iplink.c
+++ b/ip/iplink.c
@@ -1083,6 +1083,9 @@ static int iplink_modify(int cmd, unsigned int flags, int argc, char **argv)
 	if (rtnl_talk(&rth, &req.n, NULL) < 0)
 		return -2;
 
+	/* remove device from cache; next use can refresh with new data */
+	ll_drop_by_index(req.i.ifi_index);
+
 	return 0;
 }
 
-- 
2.11.0

[PATCH iproute2-next v2 3/3] Improve batch and dump times by caching link lookups

[David Ahern]

From: David Ahern <dsahern@gmail.com>

ip route uses ll_name_to_index and ll_index_to_name to convert between
device names and indices. At the moment both use for the ioctl based glibc
functions if_nametoindex and if_indextoname and does not cache the result.
When using a batch file or dumping large number of routes this means the
same device lookups can be done repeatedly adding unnecessary overhead
(socket + ioctl + close for each device lookup).

Add a new function, ll_link_get, to send a netlink based RTM_GETLINK. If
successful, cache the result in idx_head and name_head so future lookups
can re-use the entry. Update ll_name_to_index and ll_index_to_name to use
ll_link_get and only fallback to the glibc functions if it fails.

With this change the time to install 720,022 routes with 2 ecmp nexthops
where the nexthop device is given is reduced from 31.4 seconds to 19.2
seconds. A dump of those routes drops from 13.3 to 2.8 seconds.

Signed-off-by: David Ahern <dsahern@gmail.com>
---
 lib/ll_map.c | 52 +++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 51 insertions(+), 1 deletion(-)

diff --git a/lib/ll_map.c b/lib/ll_map.c
index 8e8a0b1e9c9d..2d7b65dcb8f7 100644
--- a/lib/ll_map.c
+++ b/lib/ll_map.c
@@ -152,6 +152,48 @@ static unsigned int ll_idx_a2n(const char *name)
 	return idx;
 }
 
+static int ll_link_get(const char *name, int index)
+{
+	struct {
+		struct nlmsghdr		n;
+		struct ifinfomsg	ifm;
+		char			buf[1024];
+	} req = {
+		.n.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg)),
+		.n.nlmsg_flags = NLM_F_REQUEST,
+		.n.nlmsg_type = RTM_GETLINK,
+		.ifm.ifi_index = index,
+	};
+	__u32 filt_mask = RTEXT_FILTER_VF | RTEXT_FILTER_SKIP_STATS;
+	struct rtnl_handle rth = {};
+	struct nlmsghdr *answer;
+	int rc = 0;
+
+	if (rtnl_open(&rth, 0) < 0)
+		return 0;
+
+	addattr32(&req.n, sizeof(req), IFLA_EXT_MASK, filt_mask);
+	if (name)
+		addattr_l(&req.n, sizeof(req), IFLA_IFNAME, name,
+			  strlen(name) + 1);
+
+	if (rtnl_talk(&rth, &req.n, &answer) < 0)
+		goto out;
+
+	/* add entry to cache */
+	rc  = ll_remember_index(answer, NULL);
+	if (!rc) {
+		struct ifinfomsg *ifm = NLMSG_DATA(answer);
+
+		rc = ifm->ifi_index;
+	}
+
+	free(answer);
+out:
+	rtnl_close(&rth);
+	return rc;
+}
+
 const char *ll_index_to_name(unsigned int idx)
 {
 	static char buf[IFNAMSIZ];
@@ -164,6 +206,12 @@ const char *ll_index_to_name(unsigned int idx)
 	if (im)
 		return im->name;
 
+	if (ll_link_get(NULL, idx) == idx) {
+		im = ll_get_by_index(idx);
+		if (im)
+			return im->name;
+	}
+
 	if (if_indextoname(idx, buf) == NULL)
 		snprintf(buf, IFNAMSIZ, "if%u", idx);
 
@@ -204,7 +252,9 @@ unsigned ll_name_to_index(const char *name)
 	if (im)
 		return im->index;
 
-	idx = if_nametoindex(name);
+	idx = ll_link_get(name, 0);
+	if (idx == 0)
+		idx = if_nametoindex(name);
 	if (idx == 0)
 		idx = ll_idx_a2n(name);
 	return idx;
-- 
2.11.0