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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham 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 867CDC4361B for ; Wed, 16 Dec 2020 08:22:43 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 8008123384 for ; Wed, 16 Dec 2020 08:22:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8008123384 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:43936 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kpS52-0004E4-TE for qemu-devel@archiver.kernel.org; Wed, 16 Dec 2020 03:22:40 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:44558) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kpS40-0003XV-Ir; Wed, 16 Dec 2020 03:21:36 -0500 Received: from szxga05-in.huawei.com ([45.249.212.191]:2475) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kpS3y-0007nH-7p; Wed, 16 Dec 2020 03:21:36 -0500 Received: from DGGEMS407-HUB.china.huawei.com (unknown [172.30.72.60]) by szxga05-in.huawei.com (SkyGuard) with ESMTP id 4Cwp3T2cgYzM1GY; Wed, 16 Dec 2020 16:20:37 +0800 (CST) Received: from [10.174.187.37] (10.174.187.37) by DGGEMS407-HUB.china.huawei.com (10.3.19.207) with Microsoft SMTP Server id 14.3.498.0; Wed, 16 Dec 2020 16:21:17 +0800 Subject: Re: [PATCH 1/2] accel: kvm: Fix memory waste under mismatch page size To: Peter Xu References: <20201215071948.23940-1-zhukeqian1@huawei.com> <20201215071948.23940-2-zhukeqian1@huawei.com> <20201215175719.GA112585@xz-x1> From: Keqian Zhu Message-ID: <8a23c62d-1167-d005-e98b-14507e15fbf2@huawei.com> Date: Wed, 16 Dec 2020 16:21:17 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.7.1 MIME-Version: 1.0 In-Reply-To: <20201215175719.GA112585@xz-x1> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.187.37] X-CFilter-Loop: Reflected Received-SPF: pass client-ip=45.249.212.191; envelope-from=zhukeqian1@huawei.com; helo=szxga05-in.huawei.com X-Spam_score_int: -41 X-Spam_score: -4.2 X-Spam_bar: ---- X-Spam_report: (-4.2 / 5.0 requ) BAYES_00=-1.9, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , jiangkunkun@huawei.com, qemu-devel@nongnu.org, "Dr . David Alan Gilbert" , qemu-arm@nongnu.org, Paolo Bonzini , Zenghui Yu , wanghaibin.wang@huawei.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hi Peter, On 2020/12/16 1:57, Peter Xu wrote: > On Tue, Dec 15, 2020 at 03:19:47PM +0800, Keqian Zhu wrote: >> When handle dirty log, we face qemu_real_host_page_size and >> TARGET_PAGE_SIZE. The first one is the granule of KVM dirty >> bitmap, and the second one is the granule of QEMU dirty bitmap. >> >> Generally speaking, qemu_real_host_page_size >= TARGET_PAGE_SIZE, >> so misuse TARGET_PAGE_SIZE to init kvmslot dirty_bmap may waste >> memory. For example, when qemu_real_host_page_size is 64K and >> TARGET_PAGE_SIZE is 4K, this bugfix can save 93.75% memory. >> >> Signed-off-by: Keqian Zhu >> --- >> accel/kvm/kvm-all.c | 6 +++++- >> 1 file changed, 5 insertions(+), 1 deletion(-) >> >> diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c >> index baaa54249d..c5e06288eb 100644 >> --- a/accel/kvm/kvm-all.c >> +++ b/accel/kvm/kvm-all.c >> @@ -620,8 +620,12 @@ static void kvm_memslot_init_dirty_bitmap(KVMSlot *mem) >> * too, in most cases). >> * So for now, let's align to 64 instead of HOST_LONG_BITS here, in >> * a hope that sizeof(long) won't become >8 any time soon. >> + * >> + * Note: the granule of kvm dirty log is qemu_real_host_page_size. >> + * And mem->memory_size is aligned to it (otherwise this mem can't >> + * be registered to KVM). >> */ >> - hwaddr bitmap_size = ALIGN(((mem->memory_size) >> TARGET_PAGE_BITS), >> + hwaddr bitmap_size = ALIGN(mem->memory_size / qemu_real_host_page_size, >> /*HOST_LONG_BITS*/ 64) / 8; > > Yes I think this is correct. Thanks. > > So one thing I failed to notice is cpu_physical_memory_set_dirty_lebitmap() > will "amplify" the host dirty pages into guest ones; seems we're all good then. > > Reviewed-by: Peter Xu > OK Thanks :-) One more thing, we should consider whether @start and @size is psize aligned (my second patch). Do you agree to add assert on them directly? Thanks, Keqian