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bh=owOb4Kf/LsqoT8HgH+O5+p58WWqWwBva7DaV1QMD+tU=; b=Un9tCHN1bo9nLXnH58DXgnriHu8HYQmxvQIzME2hmb3+aZI/MmQqfbpEErXTiGKDjS12dO AUqiirpmLoU7mEFthbI/oijHjXNhhQeFy5xxuSeAikElFsC2PmbZK2keLQ4OnLDC7OZBW0 64IZps4cONs3LNoiUiEQc9WV2nfJZPc= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-116-_NlNmKD4OhmgdcNeWtxbPA-1; Tue, 12 Jan 2021 09:05:38 -0500 X-MC-Unique: _NlNmKD4OhmgdcNeWtxbPA-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 6451A801B13; Tue, 12 Jan 2021 14:05:36 +0000 (UTC) Received: from dresden.str.redhat.com (ovpn-115-161.ams2.redhat.com [10.36.115.161]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D886F5B692; Tue, 12 Jan 2021 14:05:33 +0000 (UTC) Subject: Re: [PATCH v3 20/25] qapi: backup: disable copy_range by default To: Vladimir Sementsov-Ogievskiy , qemu-block@nongnu.org References: <20201026171815.13233-1-vsementsov@virtuozzo.com> <20201026171815.13233-21-vsementsov@virtuozzo.com> From: Max Reitz Message-ID: Date: Tue, 12 Jan 2021 15:05:31 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: <20201026171815.13233-21-vsementsov@virtuozzo.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mreitz@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=63.128.21.124; envelope-from=mreitz@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.251, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable 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: kwolf@redhat.com, wencongyang2@huawei.com, xiechanglong.d@gmail.com, qemu-devel@nongnu.org, armbru@redhat.com, den@openvz.org, jsnow@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 26.10.20 18:18, Vladimir Sementsov-Ogievskiy wrote: > Further commit will add a benchmark > (scripts/simplebench/bench-backup.py), which will show that backup > works better with async parallel requests (previous commit) and > disabled copy_range. So, let's disable copy_range by default. > > Signed-off-by: Vladimir Sementsov-Ogievskiy > --- > qapi/block-core.json | 2 +- > blockdev.c | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) Uh, well, er, then why did you add it as true in patch 2? Do you mean this patch as the basis for a discussion whether it should be true or false by default? I don’t have anything to contribute, though, ergo I don’t mind either way. Do you have an idea why copy offloading isn’t better? Max > diff --git a/qapi/block-core.json b/qapi/block-core.json > index 5a21c24c1d..58eb2bcb86 100644 > --- a/qapi/block-core.json > +++ b/qapi/block-core.json > @@ -1376,7 +1376,7 @@ > # Optional parameters for backup. These parameters don't affect > # functionality, but may significantly affect performance. > # > -# @use-copy-range: Use copy offloading. Default true. > +# @use-copy-range: Use copy offloading. Default false. > # > # @max-workers: Maximum number of parallel requests for the sustained background > # copying process. Doesn't influence copy-before-write operations. > diff --git a/blockdev.c b/blockdev.c > index 0ed390abe0..1ac64d8ee2 100644 > --- a/blockdev.c > +++ b/blockdev.c > @@ -2788,7 +2788,7 @@ static BlockJob *do_backup_common(BackupCommon *backup, > { > BlockJob *job = NULL; > BdrvDirtyBitmap *bmap = NULL; > - BackupPerf perf = { .use_copy_range = true, .max_workers = 64 }; > + BackupPerf perf = { .max_workers = 64 }; > int job_flags = JOB_DEFAULT; > > if (!backup->has_speed) { >