On Tue, Feb 09, 2016 at 09:11:55PM +1100, Ross Green wrote:
> Continued testing with the latest linux-4.5-rc3 release.
>
> Please find attached a copy of traces from dmesg:
>
> There is a lot more debug and trace data so hopefully this will shed
> some light on what might be happening here.
>
> My testing remains run a series of simple benchmarks, let that run to
> completion and then leave the system idle away with just a few daemons
> running.
>
> the self detected stalls in this instance turned up after a days run time.
> There were NO heavy artificial computational loads on the machine.
It does indeed look quiet on that dmesg for a good long time.
The following insanely crude not-for-mainline hack -might- be producing
good results in my testing. It will take some time before I can claim
statistically different results. But please feel free to give it a go
in the meantime. (Thanks to Al Viro for pointing me in this direction.)
Thanx, Paul
------------------------------------------------------------------------
commit 0c2c8d9fd1641809830a7a75f84dcad69936ef56
Author: Paul E. McKenney <paul...@linux.vnet.ibm.com>
Date: Tue Feb 16 15:42:36 2016 -0800
rcu: Crude exploratory hack
Signed-off-by: Paul E. McKenney <paul...@linux.vnet.ibm.com>
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 507d0ed48b97..5928e084620d 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2194,8 +2194,10 @@ static int __noreturn rcu_gp_kthread(void *arg)
READ_ONCE(rsp->gpnum),
TPS("fqswait"));
rsp->gp_state = RCU_GP_WAIT_FQS;
- ret = wait_event_interruptible_timeout(rsp->gp_wq,
- rcu_gp_fqs_check_wake(rsp, &gf), j);
+ ret = schedule_timeout_interruptible(j > 0 ? j : 1);
+ rcu_gp_fqs_check_wake(rsp, &gf);
+ // ret = wait_event_interruptible_timeout(rsp->gp_wq,
+ // rcu_gp_fqs_check_wake(rsp, &gf), j);
rsp->gp_state = RCU_GP_DOING_FQS;
/* Locking provides needed memory barriers. */
/* If grace period done, leave loop. */
