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=-0.7 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=unavailable 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 3C190C4360F for ; Sat, 30 Mar 2019 13:00:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F3F40218A6 for ; Sat, 30 Mar 2019 13:00:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=gmx.net header.i=@gmx.net header.b="HhmpQdJU" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730815AbfC3NAj (ORCPT ); Sat, 30 Mar 2019 09:00:39 -0400 Received: from mout.gmx.net ([212.227.15.15]:49805 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730784AbfC3NAi (ORCPT ); Sat, 30 Mar 2019 09:00:38 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1553950836; bh=SJulvpwaIYn6OGoiCesihBxycmrfb6p/dxTSpWEWiEs=; h=X-UI-Sender-Class:Subject:To:Cc:References:From:Date:In-Reply-To; b=HhmpQdJUFV2sw4bRkInF5oBCGjHE1T4vuuMshnlcdHd9S7bPdSwc05TL+x5wI1aR/ 7KshUJjc8qEiWMZ0vQEF5Vm9BjiOUNbjXuwJQhn1KgcKNYCCzPxCsVEb8SLcLXb6gT BV4+GrBY2YhyPQVvOgv9H1n801tuC4XRY4RCwStk= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from [0.0.0.0] ([210.140.77.29]) by mail.gmx.com (mrgmx002 [212.227.17.184]) with ESMTPSA (Nemesis) id 0MV5tl-1hSYJz4BtV-00YQt6; Sat, 30 Mar 2019 14:00:36 +0100 Subject: Re: Is it possible that certain physical disk doesn't implement flush correctly? To: Supercilious Dude Cc: "linux-btrfs@vger.kernel.org" , Linux FS Devel , linux-block@vger.kernel.org References: From: Qu Wenruo Openpgp: preference=signencrypt Autocrypt: addr=quwenruo.btrfs@gmx.com; prefer-encrypt=mutual; keydata= mQENBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAG0IlF1IFdlbnJ1byA8cXV3ZW5ydW8uYnRyZnNAZ214LmNvbT6JAVQEEwEIAD4CGwMFCwkI BwIGFQgJCgsCBBYCAwECHgECF4AWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCWdWCnQUJCWYC bgAKCRDCPZHzoSX+qAR8B/94VAsSNygx1C6dhb1u1Wp1Jr/lfO7QIOK/nf1PF0VpYjTQ2au8 ihf/RApTna31sVjBx3jzlmpy+lDoPdXwbI3Czx1PwDbdhAAjdRbvBmwM6cUWyqD+zjVm4RTG rFTPi3E7828YJ71Vpda2qghOYdnC45xCcjmHh8FwReLzsV2A6FtXsvd87bq6Iw2axOHVUax2 FGSbardMsHrya1dC2jF2R6n0uxaIc1bWGweYsq0LXvLcvjWH+zDgzYCUB0cfb+6Ib/ipSCYp 3i8BevMsTs62MOBmKz7til6Zdz0kkqDdSNOq8LgWGLOwUTqBh71+lqN2XBpTDu1eLZaNbxSI ilaVuQENBFnVga8BCACqU+th4Esy/c8BnvliFAjAfpzhI1wH76FD1MJPmAhA3DnX5JDORcga CbPEwhLj1xlwTgpeT+QfDmGJ5B5BlrrQFZVE1fChEjiJvyiSAO4yQPkrPVYTI7Xj34FnscPj /IrRUUka68MlHxPtFnAHr25VIuOS41lmYKYNwPNLRz9Ik6DmeTG3WJO2BQRNvXA0pXrJH1fN GSsRb+pKEKHKtL1803x71zQxCwLh+zLP1iXHVM5j8gX9zqupigQR/Cel2XPS44zWcDW8r7B0 q1eW4Jrv0x19p4P923voqn+joIAostyNTUjCeSrUdKth9jcdlam9X2DziA/DHDFfS5eq4fEv ABEBAAGJATwEGAEIACYWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCWdWBrwIbDAUJA8JnAAAK CRDCPZHzoSX+qA3xB/4zS8zYh3Cbm3FllKz7+RKBw/ETBibFSKedQkbJzRlZhBc+XRwF61mi f0SXSdqKMbM1a98fEg8H5kV6GTo62BzvynVrf/FyT+zWbIVEuuZttMk2gWLIvbmWNyrQnzPl mnjK4AEvZGIt1pk+3+N/CMEfAZH5Aqnp0PaoytRZ/1vtMXNgMxlfNnb96giC3KMR6U0E+siA 4V7biIoyNoaN33t8m5FwEwd2FQDG9dAXWhG13zcm9gnk63BN3wyCQR+X5+jsfBaS4dvNzvQv h8Uq/YGjCoV1ofKYh3WKMY8avjq25nlrhzD/Nto9jHp8niwr21K//pXVA81R2qaXqGbql+zo Message-ID: <16edb2d0-ee41-908f-e0bf-5c27160ccff7@gmx.com> Date: Sat, 30 Mar 2019 21:00:26 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.3 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="kg4a6AzWtIyVL1sqmPTERaraa7oGO9wNc" X-Provags-ID: V03:K1:rFjCH1ksFE+SKxkkqHCfWT+kNs4EpUlklPn7JjySsUkWFxZJN2u nBlolxrAi5SOAnt8xu/M38LR3KwwjYse9Vo9VJh7piPofhpo3HNIP5kFn3MGHmvxWQJlgG8 zp16dIpZqUENbjTIaiqOZYSRBX35tAJ9PMeaMFRIXtQSa8hEum+B/3XFwVRlgXlUdkBWVmF DAR6LNAzZ9rzTTIh3KLmg== X-UI-Out-Filterresults: notjunk:1;V03:K0:nfAcDOx4gps=:EEug02oXDsIfinqdWVBrAp x+9tBMo58G3K6Fy56VGY6UoC6P5TtWbZ6dIXeoplIICDTwtPpcTUyrMpq+GRYU/rNpopkYNYF GTXamM0hHyzPi12CZoI9sOnONaRhWkPybRUFtncjvzydzM7KIbxX+v4rlYegXP6FeLcY9Flrd BYjohPuMgH+5SzNPcSJYxPtgtbKmE5t3RJt8EMrWeRq5Hynxyraukx5gOLjmtI+1MQMFCrUjd ZSkXN1g/pXoz7lVMPudtJcJa7OE7ykgKtNxOwoB3J8T39TS//kspP+Rst4vIoErmY+ehRJHFx cko5zXYLfHkq3NGQ0VrorxMKu1ALhr/4KWZMjNC8Fuk+usah8jAEOGeLqJWTlLhHNHTWvSwty 3AbZAiCq6a2CKPhhra98omJ2tr10BToqSw3v+30ErBqsqQJo0rCkwP4l/ARvMtoDXpfV46Shk IFcfUQHVZka7+spDbQN3NW4S8UfaqRUyDiEEhjZkQTEmr9X+wXB9B9HyuwERE/8HuiLtJsmV0 CHpTIzpcfBggsbdI2baJ6mmC4S4/kYqkzbAH6ttW30dlLEJjZIAjSIqGOLOwa/NjuFdaEuBb0 xfBaJxp6T1ZTQUQaVb9gP52vfLdqjglBFK3+v/eZGyRtO+MP9yRwh5L/vqs2ic1hiBAc65j1o b2BvrMXqLyfDM0rItJqfMxe2hOn5xlWk7AWrvORq9scVVGGXqcCsZpr3E65F0Zvf57MjD6q2P wETLMAHVRqStCycRFXHKwTuBlbr3nxDSahhaMwGIcn+xkW9ZOmTKnp1+Fuf7Hgh/12WAiKZNI 2IqkekBr2BPF5FHomDt2MekmLFhsm8sqbQT8XAJ0BQn6kN2C1PrNf2AFpyYngfuYu/F001zd7 cZBxrjokcHx8IsWoj8qjIkUDJkgzwi0y/0tZIGrN4u+/AJmGu3wZsxvXvZy93o Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --kg4a6AzWtIyVL1sqmPTERaraa7oGO9wNc Content-Type: multipart/mixed; boundary="BVY78Cjyw24CWtlDcC2vARtxHRilHetjJ"; protected-headers="v1" From: Qu Wenruo To: Supercilious Dude Cc: "linux-btrfs@vger.kernel.org" , Linux FS Devel , linux-block@vger.kernel.org Message-ID: <16edb2d0-ee41-908f-e0bf-5c27160ccff7@gmx.com> Subject: Re: Is it possible that certain physical disk doesn't implement flush correctly? References: In-Reply-To: --BVY78Cjyw24CWtlDcC2vARtxHRilHetjJ Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 2019/3/30 =E4=B8=8B=E5=8D=888:57, Supercilious Dude wrote: > Hi, >=20 > This would give a false positive on any controller with a cache as all > requests would take 0ms until the cache is full and the controller has > to actually flush to disk. I'm purposing to measure the execution time of flush/fsync, not write. And if flush takes 0ms, it means it doesn't really write cached data onto disk. Thanks, Qu > I am using an HP P841 controller in my test > system and it has a 4GB cache making every IO instant unless there are > enough of them that they can't be flushed to the disks as quickly as > they come in - the latency variation is huge depending on load. >=20 > Regards >=20 > On Sat, 30 Mar 2019 at 12:34, Qu Wenruo wrote:= >> >> Hi, >> >> I'm wondering if it's possible that certain physical device doesn't >> handle flush correctly. >> >> E.g. some vendor does some complex logical in their hdd controller to >> skip certain flush request (but not all, obviously) to improve perform= ance? >> >> Do anyone see such reports? >> >> And if proves to happened before, how do we users detect such problem?= >> >> Can we just check the flush time against the write before flush call? >> E.g. write X random blocks into that device, call fsync() on it, check= >> the execution time. Repeat Y times, and compare the avg/std. >> And change X to 2X/4X/..., repeat above check. >> >> Thanks, >> Qu >> >> --BVY78Cjyw24CWtlDcC2vARtxHRilHetjJ-- --kg4a6AzWtIyVL1sqmPTERaraa7oGO9wNc Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEELd9y5aWlW6idqkLhwj2R86El/qgFAlyfaGoACgkQwj2R86El /qikNAf5AemUu9TcWp9/n90UrO5kXzqseCOFO6MsS2iGBTv8WGbQRB4acWW2ez/X /mrRc0YIORaGUwhQbOeaGV7/2EA+M+8ac/6thU/FiRxjIDJPowYmSlDcSrDk8TiM dYjNtt4MIAVM7fwTuS0T7n8iD5o68OP1YqgzpKQIUBFZPH1cLtpeVirztGkfSHko ShtZjaIT1f7s1SXK4bhgu33fXZOAerUxSflN8arGHEtqMvcem+LJ/5r+Y4f2wYS9 V11ZTWXQxY/PYwM2svDGgsJOTaVRIQwldI1qaVG7H8Zb6hLGeFaXN2xYFOJ1VqCV f2AY050Bb63ubVjzfxuaTY4btH1jRg== =3e5G -----END PGP SIGNATURE----- --kg4a6AzWtIyVL1sqmPTERaraa7oGO9wNc--