Messages in this thread | | | Date | Mon, 28 Nov 2016 15:46:39 +0900 | From | Byungchul Park <> | Subject | Re: [PATCH 2/2] rcu: Force resched_cpu when jiffies >= rcu_state.jiffies_resched |
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On Sat, Nov 26, 2016 at 04:00:46AM -0800, Paul E. McKenney wrote: > On Fri, Nov 25, 2016 at 12:34:26AM -0800, Paul E. McKenney wrote: > > On Tue, Nov 22, 2016 at 05:12:20PM +0900, Byungchul Park wrote: > > > On Wed, Nov 09, 2016 at 03:32:15PM +0900, Byungchul Park wrote: > > > > Currently rcu code forces CPU into scheduler when jiffies >= > > > > rcu_state.gp_start + jiffies_till_sched_qs, via resched_cpu(). > > > > > > > > It would be better to force CPU into scheduler when jiffies >= > > > > rcu_state.jiffies_resched, too. > > > > > > Hello, > > > > > > I think these two patches are necessary to call resched_cpu() even in > > > case of jiffies >= rcu_state.jiffies_resched, too. Am I wrong? > > > > > > It would be appriciated if you let me know if I was wrong. > > > > My current thought is that both the "if" statement and the call to > > resched_cpu() should be removed, but I am still testing and working > > through the timing. > > > > Either way, I do very much appreciate your having called my attention > > to this code! > > And the patch shown below seems to do the trick. Thoughts?
Hello,
I see.. I didn't check the log 'rcu: Stop treating in-kernel CPU-bound workloads as errors'.
If you are convinced to remove them, no objection.
Thank you, Byungchul
> > Thanx, Paul > > ------------------------------------------------------------------------ > > commit d2db185bfee894c573faebed93461e9938bdbb61 > Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > Date: Fri Nov 25 00:07:23 2016 -0800 > > rcu: Remove short-term CPU kicking > > Commit 4914950aaa12d ("rcu: Stop treating in-kernel CPU-bound workloads > as errors") added a (relatively) short-timeout call to resched_cpu(). > This was inspired by as issue that was fixed by b7e7ade34e61 ("sched/core: > Fix remote wakeups"). But given that this issue was fixed, it is time > for the current commit to remove this call to resched_cpu(). > > Reported-by: Byungchul Park <byungchul.park@lge.com> > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 5f4f80d07852..91a68e4e6671 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -1345,12 +1345,6 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp, > rdp->rsp->jiffies_resched += 5; /* Re-enable beating. */ > } > > - /* And if it has been a really long time, kick the CPU as well. */ > - if (ULONG_CMP_GE(jiffies, > - rdp->rsp->gp_start + 2 * jiffies_till_sched_qs) || > - ULONG_CMP_GE(jiffies, rdp->rsp->gp_start + jiffies_till_sched_qs)) > - resched_cpu(rdp->cpu); /* Force CPU into scheduler. */ > - > return 0; > } >
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