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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DFB57C43334 for ; Mon, 18 Jul 2022 18:26:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235978AbiGRS0m (ORCPT ); Mon, 18 Jul 2022 14:26:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34090 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235952AbiGRS0k (ORCPT ); Mon, 18 Jul 2022 14:26:40 -0400 Received: from mail-wr1-x436.google.com (mail-wr1-x436.google.com [IPv6:2a00:1450:4864:20::436]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0C28F2DA80 for ; Mon, 18 Jul 2022 11:26:39 -0700 (PDT) Received: by mail-wr1-x436.google.com with SMTP id r14so18335437wrg.1 for ; Mon, 18 Jul 2022 11:26:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=WVvDU2AL8s0vVVLudVvrgZ7AYHAWM81ym6o0jyabuV4=; b=NQ0Qe4cWnPa0u8OvVOwy8y1gQzlLdYgCBimHOn9YHa4Latcfsm8LyZWdrE80LvfLNc tXy9exDSQ3Y8+XgnPNrfrHKHIK7WHqJjLLs4ZKL3zqZf6W5Xlj4yqoBEvXm+WpLrm0JK nc+V6DOQP5AGz2bXTOdUzCzQ1YAp4XOyOvKRo9GvABDJSc2/Y2J3ShxELHCOlHxEUJpo ti2ZhHov/v/Po0RulIPBMJvjoIktisJSzAOhmFKMTwaSDEisYz9bQgmq4q0t8npT63yx Y3MItMbE+E1nY/7Zk0F2qpNd3Q0ouCIublcith4nRKDQch7WB3I3FYuxo2LIS7fvtbtL 9RXA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=WVvDU2AL8s0vVVLudVvrgZ7AYHAWM81ym6o0jyabuV4=; b=FS6SRUc/yZEPIaCRsAV9xlZSvH8Tivbyrydpf17+mZOA3dR3P50fzNG6rAS0WjDHKV PKYGeAPDyyqQZWuUUJdIfD79Lj3CN1GzP9kY1CJgFipVxVxYuIoyWIxUUMIC8YUnfYCt QGMT4x+5r4H/UoMQKd8Ys3VQ/Issi9uumx2ZSE4RQ5zKhOVfhmearmOrrLnQPH/NZA1y 1CgFzcKaNPgPxig+JqYs2/IgqHXU4bUcnfnbeUGP1Dg6/L+70wZHdkGnithxHFkA8OO1 k36wKIJuQ/nMH/iqdVxFuV5/7XPHhB+bNNwycoC7OgzTE+2nvv2AzTrFsawMase0S64Y Kg5A== X-Gm-Message-State: AJIora/KkmLUtO5iBzqS9t6Gquk10K9tEU+lDPI0GswKsQTZx5kSPm0/ 6XASASE1lWAa0ZNyIe1R9tXfUBukGlwPteGQJht0+Q== X-Google-Smtp-Source: AGRyM1vritCRy15xhjiGgheVI5ODnh3bq50PA2xHbfPtyQKW+GDSprNhKc2C1SNuU6IDGLnp3HBkT8HTXtmuIDMx9I4= X-Received: by 2002:a5d:588b:0:b0:21d:a918:65a5 with SMTP id n11-20020a5d588b000000b0021da91865a5mr24265604wrf.210.1658168797460; Mon, 18 Jul 2022 11:26:37 -0700 (PDT) MIME-Version: 1.0 References: <20220628220938.3657876-1-yosryahmed@google.com> <20220628220938.3657876-2-yosryahmed@google.com> In-Reply-To: From: Yosry Ahmed Date: Mon, 18 Jul 2022 11:26:01 -0700 Message-ID: Subject: Re: [PATCH v6 1/4] mm: add NR_SECONDARY_PAGETABLE to count secondary page table uses. To: Sean Christopherson Cc: Tejun Heo , Johannes Weiner , Zefan Li , Marc Zyngier , James Morse , Alexandru Elisei , Suzuki K Poulose , Paolo Bonzini , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Andrew Morton , Michal Hocko , Roman Gushchin , Shakeel Butt , Oliver Upton , Huang@google.com, Shaoqin , Cgroups , Linux Kernel Mailing List , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, Linux-MM Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 12, 2022 at 4:06 PM Sean Christopherson wrote: > > On Tue, Jul 12, 2022, Yosry Ahmed wrote: > > Thanks for taking another look at this! > > > > On Thu, Jul 7, 2022 at 1:59 PM Sean Christopherson wrote: > > > > > > On Tue, Jun 28, 2022, Yosry Ahmed wrote: > > > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > > > > index aab70355d64f3..13190d298c986 100644 > > > > --- a/include/linux/mmzone.h > > > > +++ b/include/linux/mmzone.h > > > > @@ -216,6 +216,7 @@ enum node_stat_item { > > > > NR_KERNEL_SCS_KB, /* measured in KiB */ > > > > #endif > > > > NR_PAGETABLE, /* used for pagetables */ > > > > + NR_SECONDARY_PAGETABLE, /* secondary pagetables, e.g. kvm shadow pagetables */ > > > > > > Nit, s/kvm/KVM, and drop the "shadow", which might be misinterpreted as saying KVM > > > pagetables are only accounted when KVM is using shadow paging. KVM's usage of "shadow" > > > is messy, so I totally understand why you included it, but in this case it's unnecessary > > > and potentially confusing. > > > > > > And finally, something that's not a nit. Should this be wrapped with CONFIG_KVM > > > (using IS_ENABLED() because KVM can be built as a module)? That could be removed > > > if another non-KVM secondary MMU user comes along, but until then, #ifdeffery for > > > stats the depend on a single feature seems to be the status quo for this code. > > > > > > > I will #ifdef the stat, but I will emphasize in the docs that is > > currently *only* used for KVM so that it makes sense if users without > > KVM don't see the stat at all. I will also remove the stat from > > show_free_areas() in mm/page_alloc.c as it seems like none of the > > #ifdefed stats show up there. > > It's might be worth getting someone from mm/ to weigh in before going through the > trouble, my suggestion/question is based purely on the existing code. Any mm folks with an opinion about this? Any preference on whether we should wrap NR_SECONDARY_PAGETABLE stats with #ifdef CONFIG_KVM for now as it is currently the only source for this stat?