Messages in this thread Patch in this message | | | Date | Mon, 13 May 2013 07:00:05 -0700 | From | "Paul E. McKenney" <> | Subject | Re: Bisected post-3.9 regression: Resume takes 5 times as much time as with v3.9 |
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On Sun, May 12, 2013 at 06:35:18PM -0700, Paul E. McKenney wrote: > On Sun, May 12, 2013 at 11:34:30PM +0200, Joerg Roedel wrote: > > On Sun, May 12, 2013 at 01:57:48PM -0700, Paul E. McKenney wrote: > > > That does look pretty extreme! If you build with CONFIG_RCU_NO_HZ=n, > > > but without the revert, do you still get the delays? > > > > With CONFIG_RCU_NO_HZ=n (and no revert) the system boots fine, no boot > > delay. I also enabled some RCU debugging options (with > > CONFIG_RCU_NO_HZ=y), but didn't see anything so far. > > OK, good -- we at least have an easy work-around while I am tracking > this down. ;-)
And could you please try out the following patch?
Thanx, Paul
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rcu: Fix comparison sense in rcu_needs_cpu()
Commit c0f4dfd4f (rcu: Make RCU_FAST_NO_HZ take advantage of numbered callbacks) introduced a bug that can result in excessively long grace periods. This bug reverse the senes of the "if" statement checking for lazy callbacks, so that RCU takes a lazy approach when there are in fact non-lazy callbacks. This can result in excessive boot, suspend, and resume times.
This commit therefore fixes the sense of this "if" statement.
Reported-by: Borislav Petkov <bp@alien8.de> Reported-by: Bjørn Mork <bjorn@mork.no> Reported-by: Joerg Roedel <joro@8bytes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index 641991d..63098a5 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -1692,7 +1692,7 @@ int rcu_needs_cpu(int cpu, unsigned long *dj) rdtp->last_accelerate = jiffies; /* Request timer delay depending on laziness, and round. */ - if (rdtp->all_lazy) { + if (!rdtp->all_lazy) { *dj = round_up(rcu_idle_gp_delay + jiffies, rcu_idle_gp_delay) - jiffies; } else { -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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