From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yk0-f170.google.com ([209.85.160.170]:34211 "EHLO mail-yk0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755245AbbFOPh2 (ORCPT ); Mon, 15 Jun 2015 11:37:28 -0400 Received: by ykfl8 with SMTP id l8so59462533ykf.1 for ; Mon, 15 Jun 2015 08:37:27 -0700 (PDT) Message-ID: <557EF12E.6000309@gmail.com> Date: Mon, 15 Jun 2015 11:37:18 -0400 From: Austin S Hemmelgarn MIME-Version: 1.0 To: Tovo Rabemanantsoa , Btrfs BTRFS Subject: Re: Bad performance with near-full FS References: <557EC95C.8020902@bordeaux.inra.fr> <20150615132915.GM6761@twin.jikos.cz> <557EE4BF.2090908@bordeaux.inra.fr> In-Reply-To: <557EE4BF.2090908@bordeaux.inra.fr> Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha1; boundary="------------ms010105040207060306030909" Sender: linux-btrfs-owner@vger.kernel.org List-ID: This is a cryptographically signed message in MIME format. --------------ms010105040207060306030909 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable On 2015-06-15 10:44, Tovo Rabemanantsoa wrote: > On 06/15/2015 03:29 PM, David Sterba wrote: >> On Mon, Jun 15, 2015 at 02:47:24PM +0200, Tovo Rabemanantsoa wrote: >>> Hi all, >>> By browsing this list's archive, I've found a thread initiated by >>> Charles Cazabon entitled: "Oddly slow read performance with near-full= >>> largish FS." >>> Actually, I'm living the same experience but with a not so large FS >>> (256GB on a SSD). Indeed, when I have less than 1GB of free space, th= e >>> applications (thunderbird, thunar ...) on the machine become awfully >>> slow but remain normal if I make some cleaning. >>> Is it due to the FS or because it's an SSD hard disk ? >> >> 1G of 256G is less than a percent. At this level of usage you can expe= ct >> slowdown on any filesystem. >> >> This could be caused by free space fragmentation and even on a SSD, th= is >> needs extra time to process. Higher number of fragments needs more >> structures to represent them and cost more CPU time, though this still= >> might not be the worst impact. >> >> AFAIK btrfs space handling logic needs to do more flushes of unwritten= >> data when the accounted free space goes below some threshold (because >> COW needs to write the data twice before it switches to the new "root"= >> pointer and can free the previous version). > > Thanks for you reply, > If I really understand, it's always a good idea to keep more than 1% of= > free space. Right ? For almost any non-COW filesystem (ext4, XFS, JFS, etc.), 1% or 100MB=20 (whichever is larger) is generally a good buffer. On BTRFS, I would say = at least 5% or 1.5G (again, whichever is larger; and if performance is a = concern, go for at least 10-20%), as BTRFS is known to have some rather=20 poor behavior when running very close to full. --------------ms010105040207060306030909 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAQAAoIIGuDCC BrQwggScoAMCAQICAxBuVTANBgkqhkiG9w0BAQ0FADB5MRAwDgYDVQQKEwdSb290IENBMR4w HAYDVQQLExVodHRwOi8vd3d3LmNhY2VydC5vcmcxIjAgBgNVBAMTGUNBIENlcnQgU2lnbmlu ZyBBdXRob3JpdHkxITAfBgkqhkiG9w0BCQEWEnN1cHBvcnRAY2FjZXJ0Lm9yZzAeFw0xNTAz MjUxOTM0MzhaFw0xNTA5MjExOTM0MzhaMGMxGDAWBgNVBAMTD0NBY2VydCBXb1QgVXNlcjEj MCEGCSqGSIb3DQEJARYUYWhmZXJyb2luN0BnbWFpbC5jb20xIjAgBgkqhkiG9w0BCQEWE2Fo ZW1tZWxnQG9oaW9ndC5jb20wggIiMA0GCSqGSIb3DQEBAQUAA4ICDwAwggIKAoICAQCdD/zW 2rRAFCLnDfXpWxU1+ODqRVUgzHvrRO7ADUxRo1CBDc3JSX5TIW2OGmQ3DAKGOACp8Z0sgxMc B05tzAZ/M7m4jajVrwwdVCdrwVGxTdAai7Kwg4ZCVfyMVhcwo8R2eW3QahBx34G0RKumK9sZ ZQSQ+zULAzpY6uz7T1sAk/erMoivRXF6u8WvOsLkOD1F/Xyv1ZccSUG5YeDgZgc0nZUBvyIp zXSHjgWerFkrxEM3y2z/Ff3eL1sgGYecV/I1F+I5S01V7Kclt/qRW10c/4JEGRcI1FmrJBPu BtMYPbg/3Y9LZROYN+mVIFxZxOfrmjfFZ96xt/TaMXo8vcEKtWcNEjhGBjEbfMUEm4aq8ygQ 4MuEcpJc8DJCHBkg2KBk13DkbU2qNepTD6Uip1C+g+KMr0nd6KOJqSH27ZuNY4xqV4hIxFHp ex0zY7mq6fV2o6sKBGQzRdI20FDYmNjsLJwjH6qJ8laxFphZnPRpBThmu0AjuBWE72GnI1oA aO+bs92MQGJernt7hByCnDO82W/ykbVz+Ge3Sax8NY0m2Xdvp6WFDY/PjD9CdaJ9nwQGsUSa N54lrZ2qMTeCI9Vauwf6U69BA42xgk65VvxvTNqji+tZ4aZbarZ7el2/QDHOb/rRwlCFplS/ z4l1f1nOrE6bnDl5RBJyW3zi74P6GwIDAQABo4IBWTCCAVUwDAYDVR0TAQH/BAIwADBWBglg hkgBhvhCAQ0ESRZHVG8gZ2V0IHlvdXIgb3duIGNlcnRpZmljYXRlIGZvciBGUkVFIGhlYWQg b3ZlciB0byBodHRwOi8vd3d3LkNBY2VydC5vcmcwDgYDVR0PAQH/BAQDAgOoMEAGA1UdJQQ5 MDcGCCsGAQUFBwMEBggrBgEFBQcDAgYKKwYBBAGCNwoDBAYKKwYBBAGCNwoDAwYJYIZIAYb4 QgQBMDIGCCsGAQUFBwEBBCYwJDAiBggrBgEFBQcwAYYWaHR0cDovL29jc3AuY2FjZXJ0Lm9y ZzAxBgNVHR8EKjAoMCagJKAihiBodHRwOi8vY3JsLmNhY2VydC5vcmcvcmV2b2tlLmNybDA0 BgNVHREELTArgRRhaGZlcnJvaW43QGdtYWlsLmNvbYETYWhlbW1lbGdAb2hpb2d0LmNvbTAN BgkqhkiG9w0BAQ0FAAOCAgEAGvl7xb42JMRH5D/vCIDYvFY3dR2FPd5kmOqpKU/fvQ8ovmJa p5N/FDrsCL+YdslxPY+AAn78PYmL5pFHTdRadT++07DPIMtQyy2qd+XRmz6zP8Il7vGcEDmO WmMLYMq4xV9s/N7t7JJp6ftdIYUcoTVChUgilDaRWMLidtslCdRsBVfUjPb1bF5Ua31diKDP e0M9/e2CU36rbcTtiNCXhptMigzuL3zJXUf2B9jyUV8pnqNEQH36fqJ7YTBLcpq3aYa2XbAH Hgx9GehJBIqwspDmhPCFZ/QmqUXCkt+XfvinQ2NzKR6P3+OdYbwqzVX8BdMeojh7Ig8x/nIx mQ+/ufstL1ZYp0bg13fyK/hPYSIBpayaC76vzWovkIm70DIDRIFLi20p/qTd7rfDYy831Hjm +lDdCECF9bIXEWFk33kA97dgQIMbf5chEmlFg8S0e4iw7LMjvRqMX3eCD8GJ2+oqyZUwzZxy S0Mx+rBld5rrN7LsXwZ671HsGqNeYbYeU25e7t7/Gcc6Bd/kPfA+adEuUGFcvUKH3trDYqNq 6mOkAd8WO/mQadlc3ztS++XDMhmIpfBre9MPAr6usqf+wc+R8Nk9KLK39kEgrqVfzc/fgf8L MaD4rHnusdg4gca6Yi+kNrm99anw7SwaBrBvULYBp7ixNRUhaYiNW4YjTrYxggShMIIEnQIB ATCBgDB5MRAwDgYDVQQKEwdSb290IENBMR4wHAYDVQQLExVodHRwOi8vd3d3LmNhY2VydC5v cmcxIjAgBgNVBAMTGUNBIENlcnQgU2lnbmluZyBBdXRob3JpdHkxITAfBgkqhkiG9w0BCQEW EnN1cHBvcnRAY2FjZXJ0Lm9yZwIDEG5VMAkGBSsOAwIaBQCgggH1MBgGCSqGSIb3DQEJAzEL BgkqhkiG9w0BBwEwHAYJKoZIhvcNAQkFMQ8XDTE1MDYxNTE1MzcxOFowIwYJKoZIhvcNAQkE MRYEFE1SC7tFGGg3URkt4P5t3/vfGMxaMGwGCSqGSIb3DQEJDzFfMF0wCwYJYIZIAWUDBAEq MAsGCWCGSAFlAwQBAjAKBggqhkiG9w0DBzAOBggqhkiG9w0DAgICAIAwDQYIKoZIhvcNAwIC AUAwBwYFKw4DAgcwDQYIKoZIhvcNAwICASgwgZEGCSsGAQQBgjcQBDGBgzCBgDB5MRAwDgYD VQQKEwdSb290IENBMR4wHAYDVQQLExVodHRwOi8vd3d3LmNhY2VydC5vcmcxIjAgBgNVBAMT GUNBIENlcnQgU2lnbmluZyBBdXRob3JpdHkxITAfBgkqhkiG9w0BCQEWEnN1cHBvcnRAY2Fj ZXJ0Lm9yZwIDEG5VMIGTBgsqhkiG9w0BCRACCzGBg6CBgDB5MRAwDgYDVQQKEwdSb290IENB MR4wHAYDVQQLExVodHRwOi8vd3d3LmNhY2VydC5vcmcxIjAgBgNVBAMTGUNBIENlcnQgU2ln bmluZyBBdXRob3JpdHkxITAfBgkqhkiG9w0BCQEWEnN1cHBvcnRAY2FjZXJ0Lm9yZwIDEG5V MA0GCSqGSIb3DQEBAQUABIICAHdL2IMHBNNNAOuu42hlaB4Cq5BDbEG1tyaI61a86nhrY2pa p4fNF9MAOdz3IixiHr8yzPDnG5Mxg/EbNR8ALeLvpiP0hQdCaX4HTtUb4J92DptVT5PT+wUH yafjofZUw6XFioYokthikk3sohq+B/WoLcDyvYFKbLdZ6dEaDqiKpYSnmojwhouvFVuidIBR QMnVrQykP+Yyr7SWrHnbdQ/u5c0GKEz8Nel1q2stgN+pC75uikAnXxAnekTCm4NOxv27h2B3 kN6X520cz6XdSrDvgQ+mO1gTuTmhgrI9Nypd1IEzROyAAw0+tnubGOy6mbaX1ag5rcwYpTlh lCr96qbof1rM3rEPM/ikhUFjUDt2LymBov2pE7XoChkcF81w2LrJcWcnku4M42p/YasK1of7 89XCJKCpoVp7ZyhOvTtxj6jG6SvhK9jogJKkcWsllXwPprE4lW+zOBQesCkqXWtK6veSLCq9 1RUOxEaBg34L31Ffcdty9XZ6xIWhmL1eJcQhed255hvv4w+4WSRdnsH1hklt1+u4U7hNJ87l 9GCjcaLDEFxvUgRkgkzlZX4e0LzZmWykxwiUFIUymtxACBu+tqG4ChZtOyztZ+wmJ8UUrkBY TEMCcSEheMFZxHPGlPbBqzBwbqBhjfOPnUV07/g5PiFg9Wt14OTVJiQTpFypAAAAAAAA --------------ms010105040207060306030909--