From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 02244CA9EAF for ; Thu, 24 Oct 2019 20:48:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CC70C21929 for ; Thu, 24 Oct 2019 20:48:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727230AbfJXUs2 (ORCPT ); Thu, 24 Oct 2019 16:48:28 -0400 Received: from mga05.intel.com ([192.55.52.43]:31973 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726973AbfJXUs2 (ORCPT ); Thu, 24 Oct 2019 16:48:28 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 24 Oct 2019 13:48:28 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.68,226,1569308400"; d="scan'208";a="201596808" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.41]) by orsmga003.jf.intel.com with ESMTP; 24 Oct 2019 13:48:26 -0700 Date: Thu, 24 Oct 2019 13:48:26 -0700 From: Sean Christopherson To: Paolo Bonzini Cc: James Hogan , Paul Mackerras , Christian Borntraeger , Janosch Frank , Radim =?utf-8?B?S3LEjW3DocWZ?= , Marc Zyngier , David Hildenbrand , Cornelia Huck , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , James Morse , Julien Thierry , Suzuki K Poulose , linux-mips@vger.kernel.org, kvm-ppc@vger.kernel.org, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 14/15] KVM: Terminate memslot walks via used_slots Message-ID: <20191024204826.GE28043@linux.intel.com> References: <20191022003537.13013-1-sean.j.christopherson@intel.com> <20191022003537.13013-15-sean.j.christopherson@intel.com> <642f73ee-9425-0149-f4f4-f56be9ae5713@redhat.com> <20191022152827.GC2343@linux.intel.com> <625e511f-bd35-3b92-0c6d-550c10fc5827@redhat.com> <20191022155220.GD2343@linux.intel.com> <5c61c094-ee32-4dcf-b3ae-092eba0159c5@redhat.com> <20191024193856.GA28043@linux.intel.com> <5320341c-1abb-610b-8f5e-090a6726a9b1@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5320341c-1abb-610b-8f5e-090a6726a9b1@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-mips-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org On Thu, Oct 24, 2019 at 10:24:09PM +0200, Paolo Bonzini wrote: > On 24/10/19 21:38, Sean Christopherson wrote: > > only > > * its new index into the array is update. > > s/update/tracked/? Ya, tracked is better. Waffled between updated and tracked, chose poorly :-) > Returns the changed memslot's > > * current index into the memslots array. > > */ > > static inline int kvm_memslot_move_backward(struct kvm_memslots *slots, > > struct kvm_memory_slot *memslot) > > { > > struct kvm_memory_slot *mslots = slots->memslots; > > int i; > > > > if (WARN_ON_ONCE(slots->id_to_index[memslot->id] == -1) || > > WARN_ON_ONCE(!slots->used_slots)) > > return -1; > > > > for (i = slots->id_to_index[memslot->id]; i < slots->used_slots - 1; i++) { > > if (memslot->base_gfn > mslots[i + 1].base_gfn) > > break; > > > > WARN_ON_ONCE(memslot->base_gfn == mslots[i + 1].base_gfn); > > > > /* Shift the next memslot forward one and update its index. */ > > mslots[i] = mslots[i + 1]; > > slots->id_to_index[mslots[i].id] = i; > > } > > return i; > > } > > > > /* > > * Move a changed memslot forwards in the array by shifting existing slots with > > * a lower GFN toward the back of the array. Note, the changed memslot itself > > * is not preserved in the array, i.e. not swapped at this time, only its new > > * index into the array is updated > > Same here? > > > * Note, slots are sorted from highest->lowest instead of lowest->highest for > > * historical reasons. > > Not just that, the largest slot (with all RAM above 4GB) is also often > at the highest address at least on x86. Ah, increasing the odds of a quick hit on lookup...but only when using a linear search. The binary search starts in the middle, so that optimization is also historical :-) > But we could sort them by size now, so I agree to call these historical > reasons. That wouldn't work with the binary search though. > The code itself is fine, thanks for the work on documenting it. > > Paolo >