From: Avi Kivity <avi@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
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
Subject: Re: [RFC PATCH v1 3/5] KVM: Add paravirt kvm_flush_tlb_others
Date: Tue, 01 May 2012 18:36:20 +0300 [thread overview]
Message-ID: <4FA002F4.8000508@redhat.com> (raw)
In-Reply-To: <1335885292.13683.150.camel@twins>
On 05/01/2012 06:14 PM, Peter Zijlstra wrote:
> On Tue, 2012-05-01 at 15:12 +0300, Avi Kivity wrote:
> >
> > What's changed is not gup_fast() but the performance of munmap(),
> > exit(), and exec(), no?
>
> If it is indeed cache related like you suggested earlier, it would be
> the allocation side of things, like fork()/mmap() that suffer since
> there's fewer hot pages about, but yes, anything creating/destroying
> page-tables.
Right.
>
> > 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?)
--
error compiling committee.c: too many arguments to function
next prev parent reply other threads:[~2012-05-01 16:08 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 [this message]
2012-05-01 16:16 ` Peter Zijlstra
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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