Re: [RFC PATCH 01/13] net: sched: allow qdiscs to handle locking

On 16-08-17 03:33 PM, Eric Dumazet wrote:

On Wed, 2016-08-17 at 12:33 -0700, John Fastabend wrote:

quoted

This patch adds a flag for queueing disciplines to indicate the stack
does not need to use the qdisc lock to protect operations. This can
be used to build lockless scheduling algorithms and improving
performance.

The flag is checked in the tx path and the qdisc lock is only taken
if it is not set. For now use a conditional if statement. Later we
could be more aggressive if it proves worthwhile and use a static key
or wrap this in a likely().

Signed-off-by: John Fastabend <redacted>
---
 include/net/pkt_sched.h   |    4 +++-
 include/net/sch_generic.h |    1 +
 net/core/dev.c            |   32 ++++++++++++++++++++++++++++----
 net/sched/sch_generic.c   |   26 ++++++++++++++++----------
 4 files changed, 48 insertions(+), 15 deletions(-)

diff --git a/include/net/pkt_sched.h b/include/net/pkt_sched.h
index 7caa99b..69540c6 100644
--- a/include/net/pkt_sched.h
+++ b/include/net/pkt_sched.h

@@ -107,8 +107,10 @@ void __qdisc_run(struct Qdisc *q);
 
 static inline void qdisc_run(struct Qdisc *q)
 {
-	if (qdisc_run_begin(q))
+	if (qdisc_run_begin(q)) {
 		__qdisc_run(q);
+		qdisc_run_end(q);
+	}
 }

Looks like you could have a separate patch, removing qdisc_run_end()
call done in __qdisc_run(q) ?

Then the 'allow qdiscs to handle locking'

Agreed that would clean this up a bit. Will do for next rev.