From: Peter Zijlstra <peterz@infradead.org>
To: Avi Kivity <avi@redhat.com>
Cc: "Nikunj A. Dadhania" <nikunj@linux.vnet.ibm.com>,
mingo@elte.hu, jeremy@goop.org, mtosatti@redhat.com,
kvm@vger.kernel.org, x86@kernel.org, vatsa@linux.vnet.ibm.com,
linux-kernel@vger.kernel.org, hpa@zytor.com,
paulmck <paulmck@linux.vnet.ibm.com>
Subject: Re: [RFC PATCH v1 3/5] KVM: Add paravirt kvm_flush_tlb_others
Date: Tue, 01 May 2012 18:16:46 +0200 [thread overview]
Message-ID: <1335889006.13683.162.camel@twins> (raw)
In-Reply-To: <4FA002F4.8000508@redhat.com>
On Tue, 2012-05-01 at 18:36 +0300, Avi Kivity wrote:
> > > What bounds the amount of memory waiting to be freed during an rcu grace
> > > period?
> >
> > Most RCU implementations don't have limits, so that could be quite a
> > lot. I think preemptible RCU has a batch limit at which point it tries
> > rather hard to force a grace period, but I'm not sure if even that
> > provides a hard limit.
> >
> > Practically though, I haven't had reports of PPC/Sparc going funny
> > because of this.
>
> It could be considered a DoS if a user is able to free page tables
> faster than rcu is able to recycle them, possibly triggering the oom
> killer (should that force a grace period before firing from the hip?)
One would think that would be a good thing, yes. However I cannot seem
to find anything like that in the current OOM killer. David, Paul, I
seem to have vague recollections of a discussion about RCU vs OOM, what
was the resolution (if anything) and would something like the below make
sense?
---
mm/oom_kill.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 46bf2ed5..244a371 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -607,6 +607,9 @@ int try_set_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask)
struct zone *zone;
int ret = 1;
+ synchronize_sched();
+ synchronize_rcu();
+
spin_lock(&zone_scan_lock);
for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
if (zone_is_oom_locked(zone)) {
next prev parent reply other threads:[~2012-05-01 16:17 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-27 16:23 [RFC PATCH v1 0/5] KVM paravirt remote flush tlb Nikunj A. Dadhania
2012-04-27 16:23 ` [RFC PATCH v1 1/5] KVM Guest: Add VCPU running/pre-empted state for guest Nikunj A. Dadhania
2012-05-01 1:03 ` Raghavendra K T
2012-05-01 3:25 ` Nikunj A Dadhania
2012-04-27 16:23 ` [RFC PATCH v1 2/5] KVM-HV: " Nikunj A. Dadhania
2012-04-27 16:24 ` [RFC PATCH v1 3/5] KVM: Add paravirt kvm_flush_tlb_others Nikunj A. Dadhania
2012-04-29 12:23 ` Avi Kivity
2012-05-01 3:34 ` Nikunj A Dadhania
2012-05-01 9:39 ` Peter Zijlstra
2012-05-01 10:47 ` Avi Kivity
2012-05-01 10:57 ` Peter Zijlstra
2012-05-01 10:59 ` Peter Zijlstra
2012-05-01 22:49 ` Jeremy Fitzhardinge
2012-05-03 14:09 ` Stefano Stabellini
2012-05-01 12:12 ` Avi Kivity
2012-05-01 14:59 ` Peter Zijlstra
2012-05-01 15:31 ` Avi Kivity
2012-05-01 15:36 ` Peter Zijlstra
2012-05-01 15:39 ` Avi Kivity
2012-05-01 15:42 ` Peter Zijlstra
2012-05-01 15:11 ` Peter Zijlstra
2012-05-01 15:33 ` Avi Kivity
2012-05-01 15:14 ` Peter Zijlstra
2012-05-01 15:36 ` Avi Kivity
2012-05-01 16:16 ` Peter Zijlstra [this message]
2012-05-01 16:43 ` Paul E. McKenney
2012-05-01 16:18 ` Peter Zijlstra
2012-05-01 16:20 ` Peter Zijlstra
2012-05-02 8:51 ` Nikunj A Dadhania
2012-05-02 10:20 ` Peter Zijlstra
2012-05-02 13:53 ` Nikunj A Dadhania
2012-05-04 4:32 ` Nikunj A Dadhania
2012-05-04 11:44 ` Srivatsa Vaddagiri
2012-05-07 3:10 ` Nikunj A Dadhania
2012-04-27 16:26 ` [RFC PATCH v1 4/5] KVM: get kvm_kick_vcpu out for pv_flush Nikunj A. Dadhania
2012-04-27 16:27 ` [RFC PATCH v1 5/5] KVM: Introduce PV kick in flush tlb Nikunj A. Dadhania
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