From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753542AbcHQRWD (ORCPT ); Wed, 17 Aug 2016 13:22:03 -0400 Received: from fw-tnat.cambridge.arm.com ([217.140.96.140]:56299 "EHLO cam-smtp0.cambridge.arm.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752163AbcHQRV2 (ORCPT ); Wed, 17 Aug 2016 13:21:28 -0400 From: Punit Agrawal To: Paolo Bonzini Cc: kvm@vger.kernel.org, Marc Zyngier , Will Deacon , linux-kernel@vger.kernel.org, Steven Rostedt , Ingo Molnar , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Subject: Re: [RFC PATCH 0/7] Add support for monitoring guest TLB operations References: <1471344312-26685-1-git-send-email-punit.agrawal@arm.com> <87fuq3tjmv.fsf@e105922-lin.cambridge.arm.com> Date: Wed, 17 Aug 2016 18:20:14 +0100 In-Reply-To: (Paolo Bonzini's message of "Wed, 17 Aug 2016 19:02:32 +0200") Message-ID: <878tvvtir5.fsf@e105922-lin.cambridge.arm.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Paolo Bonzini writes: > On 17/08/2016 19:01, Punit Agrawal wrote: >>> Can you explain what this is used for? In other words, why would this >>> be used instead of just running perf in the guest? >> >> As TLB maintenance operations are synchronised in hardware, they can >> impact performance beyond the guest. The operations generate traffic on >> the interconnect and depending on the implementation, they can also >> affect the remote TLB's translation bandwidth. >> >> These patches are useful on systems where the host and guest are >> controlled by different users - the guest could be running arbitrary >> software. >> >> Having the ability to monitor the usage of guest TLB invalidations in >> the host can be useful to diagnose performance issues on such systems. > > Are there hardware performance counters for these operations? That would have been ideal! There are PMU events defined for TLB accesses and refills but unhelpfully none of them track maintenance operations. > > Paolo > _______________________________________________ > kvmarm mailing list > kvmarm@lists.cs.columbia.edu > https://lists.cs.columbia.edu/mailman/listinfo/kvmarm