From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [RFC][PATCH 4/9] create aggregate kvm_total_used_mmu_pages value Date: Thu, 17 Jun 2010 11:43:15 +0300 Message-ID: <4C19E023.2040403@redhat.com> References: <20100615135518.BC244431@kernel.beaverton.ibm.com> <20100615135523.25D24A73@kernel.beaverton.ibm.com> <4C188FC0.3050306@redhat.com> <1276700761.6437.16878.camel@nimitz> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org To: Dave Hansen Return-path: In-Reply-To: <1276700761.6437.16878.camel@nimitz> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 06/16/2010 06:06 PM, Dave Hansen wrote: > > >>> +static inline void kvm_mod_used_mmu_pages(struct kvm *kvm, int nr) >>> +{ >>> + kvm->arch.n_used_mmu_pages += nr; >>> + kvm_total_used_mmu_pages += nr; >>> >>> >> Needs an atomic operation, since there's no global lock here. To avoid >> bouncing this cacheline around, make the variable percpu and make >> readers take a sum across all cpus. Side benefit is that you no longer >> need an atomic but a local_t, which is considerably cheaper. >> > That's a good point. All of the modifications are done under locks, but > the fast path isn't any more. I'll fix it up. > > Note, even before you moved the shrinker out of the lock, this was a problem. kvm_mod_used_mmu_pages() is called not just from the shrinker code, we zap pages for other reasons as well. -- error compiling committee.c: too many arguments to function