Le Tue, Jun 04, 2024 at 03:23:48PM -0700, Paul E. McKenney a écrit : > From: Neeraj Upadhyay <Neeraj.Upadhyay@xxxxxxx> > > When all wait heads are in use, which can happen when > rcu_sr_normal_gp_cleanup_work()'s callback processing > is slow, any new synchronize_rcu() user's rcu_synchronize > node's processing is deferred to future GP periods. This > can result in long list of synchronize_rcu() invocations > waiting for full grace period processing, which can delay > freeing of memory. Mitigate this problem by using first > node in the list as wait tail when all wait heads are in use. > While methods to speed up callback processing would be needed > to recover from this situation, allowing new nodes to complete > their grace period can help prevent delays due to a fixed > number of wait head nodes. > > Signed-off-by: Neeraj Upadhyay <Neeraj.Upadhyay@xxxxxxx> > Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx> IIRC we agreed that this patch could be a step too far that made an already not so simple state machine even less simple, breaking the wait_head based flow. Should we postpone this change until it is observed that a workqueue not being scheduled for 5 grace periods is a real issue? Thanks.
