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[83.57.175.68]) by smtp.gmail.com with ESMTPSA id p4sm10591045wma.36.2021.02.11.15.49.39 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 11 Feb 2021 15:49:39 -0800 (PST) Subject: Re: [PATCH v2 1/2] block: Explicit null-co uses 'read-zeroes=false' To: Eric Blake , qemu-devel@nongnu.org References: <20210211142656.3818078-1-philmd@redhat.com> <20210211142656.3818078-2-philmd@redhat.com> <40f42cc8-521f-5090-63cf-b4549be43905@redhat.com> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Message-ID: <37752c95-95cf-390d-3dfd-b1919e0352bc@redhat.com> Date: Fri, 12 Feb 2021 00:49:38 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <40f42cc8-521f-5090-63cf-b4549be43905@redhat.com> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=philmd@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=63.128.21.124; envelope-from=philmd@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.569, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.119, 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: Fam Zheng , Laurent Vivier , Thomas Huth , qemu-block@nongnu.org, Markus Armbruster , Wainer dos Santos Moschetta , Max Reitz , Alexander Bulekov , Bandan Das , Stefan Hajnoczi , Cleber Rosa , Paolo Bonzini , Kevin Wolf Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 2/11/21 11:40 PM, Eric Blake wrote: > On 2/11/21 8:26 AM, Philippe Mathieu-Daudé wrote: >> We are going to switch the 'null-co' default 'read-zeroes' value >> from FALSE to TRUE in the next commit. First explicit the FALSE >> value when it is not set. > > Grammar suggestion, along with a suggestion for an additional sentence > to make the intent of this commit clearer: > > As a first step, request an explicit FALSE value rather than relying on > the defaults. This is intended to be a purely mechanical adjustment for > no performance behavior in the tests; later patches may then flip or > elide the explicit choice for tests where performance does not matter. > >> >> Suggested-by: Eric Blake >> Signed-off-by: Philippe Mathieu-Daudé >> --- >> - Missing: 056 & 155. I couldn't figure out the proper syntax, >> any help welcomed... > > 056 - looks like just one line: > self.vm = > iotests.VM().add_drive_raw("file=blkdebug::null-co://,id=drive0,align=65536,driver=blkdebug") > > the best way to add it here would be rewriting that line to use blockdev > syntax rather than blkdebug: URI syntax. The other question is whether > it is a noticeable time difference when the default is flipped in 2/2. > > 155 - looks like several uses such as: > > class TestBlockdevMirrorForcedBacking(MirrorBaseClass): > cmd = 'blockdev-mirror' > existing = True > target_backing = None > target_blockdev_backing = { 'driver': 'null-co' } > target_real_backing = 'null-co://' > > >> - I'm unsure about 162, this doesn't seem to use the null-co >> driver but rather testing global syntax. > > Concur; I don't see any reason to worry about this one (but mentioning > it in the commit message can't hurt in case someone asks later) > > # blkdebug expects all of its arguments to be strings, but its > # bdrv_refresh_filename() implementation should not assume that they > have been > # passed as strings in the original options QDict. > # So this should emit blkdebug:42:null-co:// as the filename: > touch 42 > $QEMU_IMG info 'json:{"driver": "blkdebug", "config": 42, > "image.driver": "null-co"}' \ > > >> --- >> docs/devel/testing.rst | 14 +++++++------- >> tests/qtest/fuzz/generic_fuzz_configs.h | 11 ++++++----- >> tests/test-bdrv-drain.c | 10 ++++++++-- >> tests/acceptance/virtio_check_params.py | 2 +- >> tests/perf/block/qcow2/convert-blockstatus | 6 +++--- >> tests/qemu-iotests/040 | 2 +- > > You did a pretty good hunt for culprits! > >> tests/qemu-iotests/041 | 12 ++++++++---- >> tests/qemu-iotests/051 | 2 +- >> tests/qemu-iotests/051.out | 2 +- >> tests/qemu-iotests/051.pc.out | 4 ++-- > > and for the fallout to the iotests. > > I did not audit for which tests are easy candidates for dropping the > explicit read-zeroes=false (that is, where the extra time in allowing > the flipped default doesn't penalize the test), but am okay giving this > patch: > > Reviewed-by: Eric Blake Thanks for your help. I'll address your comments and respin. Regards, Phil.