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 C34E2C04FFE for ; Wed, 20 Sep 2023 21:12:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229877AbjITVMm (ORCPT ); Wed, 20 Sep 2023 17:12:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43410 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229709AbjITVMm (ORCPT ); Wed, 20 Sep 2023 17:12:42 -0400 Received: from out-217.mta1.migadu.com (out-217.mta1.migadu.com [IPv6:2001:41d0:203:375::d9]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3B2F49E for ; Wed, 20 Sep 2023 14:12:36 -0700 (PDT) Date: Wed, 20 Sep 2023 21:12:29 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1695244354; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=EoUJ+vC7dyHc4K1PhRWk1cP4axcoR/iMI8O3D2rH4lY=; b=nRiL2bpy2TvTJglYvs33qdCvn+bntJIqeFLZAQ008Kh+KjusCOOUq6O7scKrO2N6lGZ447 wdyM74RKMJ8MiwBGBne8n/vHE2RLBbEhrWTqojIiycJD+VQbnINfiM5f19woTYK0+D1dMX aj0Js4mG+/ntjHCDt8mp6aXb0/VaF9c= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Oliver Upton To: Shameerali Kolothum Thodi Cc: "kvmarm@lists.linux.dev" , "kvm@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "maz@kernel.org" , "will@kernel.org" , "catalin.marinas@arm.com" , "james.morse@arm.com" , "suzuki.poulose@arm.com" , yuzenghui , zhukeqian , Jonathan Cameron , Linuxarm Subject: Re: [RFC PATCH v2 0/8] KVM: arm64: Implement SW/HW combined dirty log Message-ID: References: <20230825093528.1637-1-shameerali.kolothum.thodi@huawei.com> <14eb2648eb594dd9a46a179733cee0df@huawei.com> <853b333084c4462a870bb2a37ec65935@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <853b333084c4462a870bb2a37ec65935@huawei.com> X-Migadu-Flow: FLOW_OUT Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Mon, Sep 18, 2023 at 09:55:22AM +0000, Shameerali Kolothum Thodi wrote: [...] > > Sorry, this was rather nonspecific. I was describing the pre-copy > > strategies we're using at Google (out of tree). We're carrying patches > > to use EPT D-bit for exitless dirty tracking. > > Just curious, how does it handle the overheads associated with scanning for > dirty pages and the convergence w.r.t high rate of dirtying in exitless mode? A pool of kthreads, which really isn't a good solution at all. The 'better' way to do it would be to add some back pressure to the guest such that your pre-copy transfer can converge with the guest and use the freed up CPU time to manage the dirty state. But hopefully we can make that a userspace issue. -- Thanks, Oliver