From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-213.mta1.migadu.com (out-213.mta1.migadu.com [95.215.58.213]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 99EFE41A80 for ; Wed, 20 Sep 2023 21:12:36 +0000 (UTC) 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> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: 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 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 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 00ABFC04FFE for ; Wed, 20 Sep 2023 21:13:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=PmxnXRDXw5hk1E3VtvFKk0yD858YyB5bGjezIgn9790=; b=0Ntis6W7leSTuI DLoQXp7sxrucx2CWBVVyeX3UwF2JbLJKzYBzgOGAenQOwkqgeiJFujp+IgLhOVkZsLrl03Gv428w1 q9banpImCUniW0fyHhwgxewBUiWH6a5hT5d/KpN41FAZRJKG1od4d9BoCUHxYN6nfzo5a3bjtkWMA /yK6oqI8UcxUYRPtwM33CguwpwbH6UNQFlKSoKEpSdfMHXI5HO3dnbKCAFDaYZHc/dzNhNOulbxH0 Kt4/SNJPQov0HZsqBS9iRbrA1qStzKaGX2AvTttMBnIq9fGc59wDJzPiiDSQsDnmjnymAoW3JI5XF CCi2tNE4vKReqD7Rltiw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1qj4V4-004Epc-06; Wed, 20 Sep 2023 21:12:46 +0000 Received: from out-221.mta1.migadu.com ([2001:41d0:203:375::dd]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1qj4V0-004Eof-37 for linux-arm-kernel@lists.infradead.org; Wed, 20 Sep 2023 21:12:44 +0000 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-Disposition: inline In-Reply-To: <853b333084c4462a870bb2a37ec65935@huawei.com> X-Migadu-Flow: FLOW_OUT X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230920_141243_171743_1EA9ABC6 X-CRM114-Status: GOOD ( 10.77 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.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 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel