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[88.147.40.42]) by smtp.gmail.com with ESMTPSA id u7sm13503722wmg.25.2019.05.22.02.09.28 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 22 May 2019 02:09:28 -0700 (PDT) From: Paolo Valente Message-Id: <686D6469-9DE7-4738-B92A-002144C3E63E@linaro.org> Content-Type: multipart/signed; boundary="Apple-Mail=_3DB989E2-874B-47C2-B6CC-3F154F79180F"; protocol="application/pgp-signature"; micalg=pgp-sha256 Mime-Version: 1.0 (Mac OS X Mail 12.4 \(3445.104.8\)) Subject: Re: CFQ idling kills I/O performance on ext4 with blkio cgroup controller Date: Wed, 22 May 2019 11:09:26 +0200 In-Reply-To: Cc: linux-fsdevel@vger.kernel.org, linux-block , linux-ext4@vger.kernel.org, cgroups@vger.kernel.org, kernel list , Jens Axboe , Jan Kara , jmoyer@redhat.com, Theodore Ts'o , amakhalov@vmware.com, anishs@vmware.com, srivatsab@vmware.com To: "Srivatsa S. Bhat" References: <8d72fcf7-bbb4-2965-1a06-e9fc177a8938@csail.mit.edu> <1812E450-14EF-4D5A-8F31-668499E13652@linaro.org> <46c6a4be-f567-3621-2e16-0e341762b828@csail.mit.edu> <07D11833-8285-49C2-943D-E4C1D23E8859@linaro.org> <5B6570A2-541A-4CF8-98E0-979EA6E3717D@linaro.org> <2CB39B34-21EE-4A95-A073-8633CF2D187C@linaro.org> <0e3fdf31-70d9-26eb-7b42-2795d4b03722@csail.mit.edu> X-Mailer: Apple Mail (2.3445.104.8) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org --Apple-Mail=_3DB989E2-874B-47C2-B6CC-3F154F79180F Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii > Il giorno 22 mag 2019, alle ore 10:05, Paolo Valente = ha scritto: >=20 >=20 >=20 >> Il giorno 22 mag 2019, alle ore 00:51, Srivatsa S. Bhat = ha scritto: >>=20 >> [ Resending this mail with a dropbox link to the traces (instead >> of a file attachment), since it didn't go through the last time. ] >>=20 >> On 5/21/19 10:38 AM, Paolo Valente wrote: >>>=20 >>>> So, instead of only sending me a trace, could you please: >>>> 1) apply this new patch on top of the one I attached in my previous = email >>>> 2) repeat your test and report results >>>=20 >>> One last thing (I swear!): as you can see from my script, I tested = the >>> case low_latency=3D0 so far. So please, for the moment, do your = test >>> with low_latency=3D0. You find the whole path to this parameter in, >>> e.g., my script. >>>=20 >> No problem! :) Thank you for sharing patches for me to test! >>=20 >> I have good news :) Your patch improves the throughput significantly >> when low_latency =3D 0. >>=20 >> Without any patch: >>=20 >> dd if=3D/dev/zero of=3D/root/test.img bs=3D512 count=3D10000 = oflag=3Ddsync >> 10000+0 records in >> 10000+0 records out >> 5120000 bytes (5.1 MB, 4.9 MiB) copied, 58.0915 s, 88.1 kB/s >>=20 >>=20 >> With both patches applied: >>=20 >> dd if=3D/dev/zero of=3D/root/test0.img bs=3D512 count=3D10000 = oflag=3Ddsync >> 10000+0 records in >> 10000+0 records out >> 5120000 bytes (5.1 MB, 4.9 MiB) copied, 3.87487 s, 1.3 MB/s >>=20 >> The performance is still not as good as mq-deadline (which achieves >> 1.6 MB/s), but this is a huge improvement for BFQ nonetheless! >>=20 >> A tarball with the trace output from the 2 scenarios you requested, >> one with only the debug patch applied = (trace-bfq-add-logs-and-BUG_ONs), >> and another with both patches applied (trace-bfq-boost-injection) is >> available here: >>=20 >> https://www.dropbox.com/s/pdf07vi7afido7e/bfq-traces.tar.gz?dl=3D0 >>=20 >=20 > Hi Srivatsa, > I've seen the bugzilla you've created. I'm a little confused on how > to better proceed. Shall we move this discussion to the bugzilla, or > should we continue this discussion here, where it has started, and > then update the bugzilla? >=20 Ok, I've received some feedback on this point, and I'll continue the discussion here. Then I'll report back on the bugzilla. First, thank you very much for testing my patches, and, above all, for sharing those huge traces! According to the your traces, the residual 20% lower throughput that you record is due to the fact that the BFQ injection mechanism takes a few hundredths of seconds to stabilize, at the beginning of the workload. During that setup time, the throughput is equal to the dreadful ~60-90 = KB/s that you see without this new patch. After that time, there seems to be no loss according to the trace. The problem is that a loss lasting only a few hundredths of seconds is however not negligible for a write workload that lasts only 3-4 seconds. Could you please try writing a larger file? In addition, I wanted to ask you whether you measured BFQ throughput with traces disabled. This may make a difference. After trying writing a larger file, you can try with low_latency on. On my side, it causes results to become a little unstable across repetitions (which is expected). Thanks, Paolo > Let me know, > Paolo >=20 >> Thank you! >>=20 >> Regards, >> Srivatsa >> VMware Photon OS --Apple-Mail=_3DB989E2-874B-47C2-B6CC-3F154F79180F Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename=signature.asc Content-Type: application/pgp-signature; name=signature.asc Content-Description: Message signed with OpenPGP -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEpYoduex+OneZyvO8OAkCLQGo9oMFAlzlEcYACgkQOAkCLQGo 9oNJ3Q//Sg7XcjVaaf3n1snyQH02p5UlfydhClnm/MruZLDVt8oB0HJMiP23IUwC m3LhFiSCOgV2+knSjwbk3jtUR2tnvkBVcko/G2luqxPxJrq7v5GjSfEb/hLjgwpB U7ufv14kR2EbE5C+2Qz9/JMsco9EOnGpCr3hO6/iWYkGBScu79iqoIH3wUuRdpg2 m1SkP/NWcrtc4kydA09RHjQTeSFNLZeO9PLjAVR6tkUGEmwopqqE+toWYiqBtScs 1Bf+eoQqAIxDr2OA98HpvUN6hYQxsDTNNbNn04wRLb+fK2BChcDDkM5MaJ/09YpK s4DXMjs+ifvLi3PTTbAscjujOLDnsWaAmmY/rufox97lXPxxt6UySkdENFUBFLNd bWvWMAb438p0Pz3hwNrU/tZh+nGYvqQT11oXq1Dlrks6kXS+iEfuZms34vz9tGfr r8XlqfImvkUSn4NI7YocIyqg76Rf2t5VGr59mR+7cN58y/vBbkPr7FkjXl/1LfGm bQsHL+D+NHb7NXgX91Jp97bKIX0yHnXdxrGZsjCH27C/HOzhtrncBzjcU2TPMEw+ T9JmOJf8G2vXfR5G5voKot2wX1qZ9Nnpd9T5U0rHd4ami2oiOv0BV1rAkbjaH5Qd RcWZyGaSRBpzHuQQPi/jG18YzPbNt6szIflujQfdX38sPRcTXyk= =qTPQ -----END PGP SIGNATURE----- --Apple-Mail=_3DB989E2-874B-47C2-B6CC-3F154F79180F--