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 us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 6D067C43334 for ; Tue, 14 Jun 2022 14:54:48 +0000 (UTC) Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-189-DQ9Xo27PMCypFnHQOntKbw-1; Tue, 14 Jun 2022 10:54:44 -0400 X-MC-Unique: DQ9Xo27PMCypFnHQOntKbw-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 6400A38173C0; Tue, 14 Jun 2022 14:54:41 +0000 (UTC) Received: from mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com (unknown [10.30.29.100]) by smtp.corp.redhat.com (Postfix) with ESMTP id 101AD9D7F; Tue, 14 Jun 2022 14:54:36 +0000 (UTC) Received: from mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com (localhost [IPv6:::1]) by mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com (Postfix) with ESMTP id B27A11947070; Tue, 14 Jun 2022 14:54:35 +0000 (UTC) Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) by mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com (Postfix) with ESMTP id E41ED1947067 for ; Tue, 14 Jun 2022 14:54:33 +0000 (UTC) Received: by smtp.corp.redhat.com (Postfix) id D13D8492CA4; Tue, 14 Jun 2022 14:54:33 +0000 (UTC) Received: from mimecast-mx02.redhat.com (mimecast02.extmail.prod.ext.rdu2.redhat.com [10.11.55.18]) by smtp.corp.redhat.com (Postfix) with ESMTPS id CD3C3492C3B for ; Tue, 14 Jun 2022 14:54:33 +0000 (UTC) Received: from us-smtp-1.mimecast.com (us-smtp-delivery-1.mimecast.com [205.139.110.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id B9BCF801756 for ; Tue, 14 Jun 2022 14:54:33 +0000 (UTC) Received: from plutone.assyoma.it (host195-56-237-212.serverdedicati.aruba.it [212.237.56.195]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-410-0qHBzE7SNbCJhx_VtD-kKw-1; Tue, 14 Jun 2022 10:54:31 -0400 X-MC-Unique: 0qHBzE7SNbCJhx_VtD-kKw-1 Received: from webmail.assyoma.it (localhost [IPv6:::1]) by plutone.assyoma.it (Postfix) with ESMTPA id 508C71C9FD71; Tue, 14 Jun 2022 16:54:28 +0200 (CEST) MIME-Version: 1.0 Date: Tue, 14 Jun 2022 16:54:28 +0200 From: Gionatan Danti To: Zhiyong Ye In-Reply-To: <5970db8d-462f-0e35-741c-fa0fdc188fa2@bytedance.com> References: <9c22b11a-b539-1974-7994-6835eea82bfd@bytedance.com> <8baee796-9bfb-47a8-1661-7e94437826c9@bytedance.com> <5970db8d-462f-0e35-741c-fa0fdc188fa2@bytedance.com> User-Agent: Roundcube Webmail/1.4.13 Message-ID: X-Sender: g.danti@assyoma.it X-Mimecast-Impersonation-Protect: Policy=CLT - Impersonation Protection Definition; Similar Internal Domain=false; Similar Monitored External Domain=false; Custom External Domain=false; Mimecast External Domain=false; Newly Observed Domain=false; Internal User Name=false; Custom Display Name List=false; Reply-to Address Mismatch=false; Targeted Threat Dictionary=false; Mimecast Threat Dictionary=false; Custom Threat Dictionary=false X-Scanned-By: MIMEDefang 2.85 on 10.11.54.9 Subject: Re: [linux-lvm] Why is the performance of my lvmthin snapshot so poor X-BeenThere: linux-lvm@redhat.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: LVM general discussion and development Cc: LVM general discussion and development Errors-To: linux-lvm-bounces@redhat.com Sender: "linux-lvm" X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=linux-lvm-bounces@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Il 2022-06-14 15:29 Zhiyong Ye ha scritto: > The reason for this may be that when the volume creates a snapshot, > each write to an existing block will cause a COW (Copy-on-write), and > the COW is a copy of the entire data block in chunksize, for example, > when the chunksize is 64k, even if only 4k of data is written, the > entire 64k data block will be copied. I'm not sure if I understand > this correctly. Yes, in your case, the added copies are lowering total available IOPs. But note how the decrease is sub-linear (from 64K to 1M you have a 16x increase in chunk size but "only" a 10x hit in IOPs): this is due to the lowered metadata overhead. A last try: if you can, please regenerate your thin volume with 64K chunks and set fio to execute 64K requests. Lets see if LVM is at least smart enough to avoid coping a to-be-completely-overwritten chunks. Regards. -- Danti Gionatan Supporto Tecnico Assyoma S.r.l. - www.assyoma.it email: g.danti@assyoma.it - info@assyoma.it GPG public key ID: FF5F32A8 _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://listman.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/