From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH v2] KVM: MMU: Fix mmu_shrink() so that it can free mmu pages as intended Date: Wed, 22 Aug 2012 15:27:30 +0300 Message-ID: <5034D032.4010707@redhat.com> References: <20120820183539.6604a317.yoshikawa.takuya@oss.ntt.co.jp> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: mtosatti@redhat.com, kvm@vger.kernel.org, gleb@redhat.com To: Takuya Yoshikawa Return-path: Received: from mx1.redhat.com ([209.132.183.28]:59451 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932094Ab2HVM1g (ORCPT ); Wed, 22 Aug 2012 08:27:36 -0400 In-Reply-To: <20120820183539.6604a317.yoshikawa.takuya@oss.ntt.co.jp> Sender: kvm-owner@vger.kernel.org List-ID: On 08/20/2012 12:35 PM, Takuya Yoshikawa wrote: > Although the possible race described in > > commit 85b7059169e128c57a3a8a3e588fb89cb2031da1 > KVM: MMU: fix shrinking page from the empty mmu > > was correct, the real cause of that issue was a more trivial bug of > mmu_shrink() introduced by > > commit 1952639665e92481c34c34c3e2a71bf3e66ba362 > KVM: MMU: do not iterate over all VMs in mmu_shrink() > > Here is the bug: > > if (kvm->arch.n_used_mmu_pages > 0) { > if (!nr_to_scan--) > break; > continue; > } > > We skip VMs whose n_used_mmu_pages is not zero and try to shrink others: > in other words we try to shrink empty ones by mistake. > > This patch reverses the logic so that mmu_shrink() can free pages from > the first VM whose n_used_mmu_pages is not zero. Note that we also add > comments explaining the role of nr_to_scan which is not practically > important now, hoping this will be improved in the future. > > Signed-off-by: Takuya Yoshikawa Thanks, applied to master for 3.6. -- error compiling committee.c: too many arguments to function