From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752210AbaHTPb2 (ORCPT ); Wed, 20 Aug 2014 11:31:28 -0400 Received: from mx1.redhat.com ([209.132.183.28]:58322 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751565AbaHTPbZ (ORCPT ); Wed, 20 Aug 2014 11:31:25 -0400 Date: Wed, 20 Aug 2014 17:31:16 +0200 From: Radim =?utf-8?B?S3LEjW3DocWZ?= To: Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Gleb Natapov , Raghavendra KT , Vinod Chegu , Hui-Zhi Subject: Re: [PATCH 9/9] KVM: VMX: automatic PLE window maximum Message-ID: <20140820153115.GA20453@potion.brq.redhat.com> References: <1408480536-8240-1-git-send-email-rkrcmar@redhat.com> <1408480536-8240-10-git-send-email-rkrcmar@redhat.com> <53F44B40.6060806@redhat.com> <20140820124112.GC28873@potion.brq.redhat.com> <53F49F80.1090408@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <53F49F80.1090408@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2014-08-20 15:15+0200, Paolo Bonzini: > Il 20/08/2014 14:41, Radim Krčmář ha scritto: > >> > if (ple_window_grow < 1 || ple_window_actual_max < ple_window) > >> > new = ple_window; > >> > else if (ple_window_grow < ple_window) > >> > new = max(ple_window_actual_max, old) * ple_window_grow; > >> > else > >> > new = max(ple_window_actual_max, old) + ple_window_grow; > > Oh, I like that this can get rid of all overflows, ple_window_actual_max > > (PW_effective_max?) is going to be set to > > "ple_window_max [/-] ple_window_grow" in v2. > > > >> > (I think the || in the first "if" can be eliminated with some creativity > >> > in clamp_ple_window_max). > > To do it, we'll want to intercept changes to ple_window as well. > > (I disliked this patch a lot even before :) > > What about setting ple_window_actual_max to 0 if ple_window_grow is 0 > (instead of just returning)? > > Then the "if (ple_window_actual_max < ple_window)" will always fail and > you'll go through "new = ple_window". But perhaps it's more gross and > worthless than creative. :) That code can't use PW directly, because PW_actual_max needs to be one PW_grow below PW_max, so I'd rather enforce minimal PW_actual_max. Btw. without extra code, we are still going to overflow on races when changing PW_grow, should they be covered as well? (+ There is a bug in this patch -- clamp_ple_window_max() should be after param_set_int() ... damned unreviewed last-second changes.)