From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcelo Tosatti Subject: Re: [PATCH v3] KVM: MMU: Don't use RCU for lockless shadow walking Date: Wed, 16 May 2012 16:08:45 -0300 Message-ID: <20120516190843.GB25004@amt.cnet> References: <1336999446-20398-1-git-send-email-avi@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Xiao Guangrong , kvm@vger.kernel.org To: Avi Kivity Return-path: Received: from mx1.redhat.com ([209.132.183.28]:28017 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964799Ab2EPTnj (ORCPT ); Wed, 16 May 2012 15:43:39 -0400 Content-Disposition: inline In-Reply-To: <1336999446-20398-1-git-send-email-avi@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Mon, May 14, 2012 at 03:44:06PM +0300, Avi Kivity wrote: > Using RCU for lockless shadow walking can increase the amount of memory > in use by the system, since RCU grace periods are unpredictable. We also > have an unconditional write to a shared variable (reader_counter), which > isn't good for scaling. > > Replace that with a scheme similar to x86's get_user_pages_fast(): disable > interrupts during lockless shadow walk to force the freer > (kvm_mmu_commit_zap_page()) to wait for the TLB flush IPI to find the > processor with interrupts enabled. > > We also add a new vcpu->mode, READING_SHADOW_PAGE_TABLES, to prevent > kvm_flush_remote_tlbs() from avoiding the IPI. > > Signed-off-by: Avi Kivity Applied, thanks.