From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wanpeng Li Subject: Re: [RFC PATCH 1/4] KVM: x86: Split the APIC from the rest of IRQCHIP. Date: Fri, 15 May 2015 13:03:02 +0800 Message-ID: <20150515050302.GA7255@kernel> References: <1431481652-27268-1-git-send-email-srutherford@google.com> <555303CC.5030507@redhat.com> <20150513221001.GA23867@google.com> Reply-To: Wanpeng Li Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "Wu, Feng" , Steve Rutherford , Paolo Bonzini , "kvm@vger.kernel.org" To: Andrew Honig Return-path: Received: from mga02.intel.com ([134.134.136.20]:48722 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752332AbbEOFUw (ORCPT ); Fri, 15 May 2015 01:20:52 -0400 Content-Disposition: inline In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: On Thu, May 14, 2015 at 12:29:21PM -0700, Andrew Honig wrote: >> >> BTW, what is the purpose of this series. If I understand it correctly, you only want to >> use the in-kernel lapic and leave the others (pic, ioapic) in userspace, what is the >> benefit of it? > >The purpose is to achieve the security benefit of removing some of the >interrupt handling into userspace, without incurring a significant >performance penalty. If you move the entire IRQCHIP into userspace, >we've seen perf impacts from 15-200% depending on the workload. With >this patch series, we're seeing perf penalty <1% on our tests (TCP_RR Why keep pic and ioapic in kernel space not get obvious benefit, what's the bottleneck? Regards, Wanpeng Li >latency, TCP throughput, and Disk I/O). See >(https://lwn.net/Articles/619332/) > >> >> Thanks, >> Feng >> >>> >-- >To unsubscribe from this list: send the line "unsubscribe kvm" in >the body of a message to majordomo@vger.kernel.org >More majordomo info at http://vger.kernel.org/majordomo-info.html