diff mbox series

[net-next,v2,1/5] rtnl: add helper to check if rtnl group has listeners

Message ID 20231204203907.413435-2-pctammela@mojatatu.com (mailing list archive)
State Superseded
Delegated to: Netdev Maintainers
Headers show
Series net/sched: conditional notification of events for cls and act | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for net-next
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 4579 this patch: 4579
netdev/cc_maintainers warning 1 maintainers not CCed: martin@strongswan.org
netdev/build_clang success Errors and warnings before: 1333 this patch: 1333
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 4834 this patch: 4834
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 11 lines checked
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0

Commit Message

Pedro Tammela Dec. 4, 2023, 8:39 p.m. UTC 
From: Jamal Hadi Salim <jhs@mojatatu.com>

As of today, rtnl code creates a new skb and unconditionally fills and
broadcasts it to the relevant group. For most operations this is okay
and doesn't waste resources in general.

When operations are done without the rtnl_lock, as in tc-flower, such
skb allocation, message fill and no-op broadcasting can happen in all
cores of the system, which contributes to system pressure and wastes
precious cpu cycles when no one will receive the built message.

Introduce this helper so rtnetlink operations can simply check if someone
is listening and then proceed if necessary.

Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Victor Nogueira <victor@mojatatu.com>
Signed-off-by: Pedro Tammela <pctammela@mojatatu.com>
---
 include/linux/rtnetlink.h | 7 +++++++
 1 file changed, 7 insertions(+)

Comments

Jiri Pirko Dec. 5, 2023, 11:50 a.m. UTC | #1 
Mon, Dec 04, 2023 at 09:39:03PM CET, pctammela@mojatatu.com wrote:
>From: Jamal Hadi Salim <jhs@mojatatu.com>
>
>As of today, rtnl code creates a new skb and unconditionally fills and
>broadcasts it to the relevant group. For most operations this is okay
>and doesn't waste resources in general.
>
>When operations are done without the rtnl_lock, as in tc-flower, such
>skb allocation, message fill and no-op broadcasting can happen in all
>cores of the system, which contributes to system pressure and wastes
>precious cpu cycles when no one will receive the built message.
>
>Introduce this helper so rtnetlink operations can simply check if someone
>is listening and then proceed if necessary.
>
>Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
>Signed-off-by: Victor Nogueira <victor@mojatatu.com>
>Signed-off-by: Pedro Tammela <pctammela@mojatatu.com>

Reviewed-by: Jiri Pirko <jiri@nvidia.com>
diff mbox series

Patch

diff --git a/include/linux/rtnetlink.h b/include/linux/rtnetlink.h
index 3d6cf306cd55..a7d757e96c55 100644
--- a/include/linux/rtnetlink.h
+++ b/include/linux/rtnetlink.h
@@ -130,4 +130,11 @@  extern int ndo_dflt_bridge_getlink(struct sk_buff *skb, u32 pid, u32 seq,
 
 extern void rtnl_offload_xstats_notify(struct net_device *dev);
 
+static inline int rtnl_has_listeners(const struct net *net, u32 group)
+{
+	struct sock *rtnl = net->rtnl;
+
+	return netlink_has_listeners(rtnl, group);
+}
+
 #endif	/* __LINUX_RTNETLINK_H */