From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mailgw-01.dd24.net ([193.46.215.41]:45163 "EHLO mailgw-01.dd24.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753894AbbK0RDO (ORCPT ); Fri, 27 Nov 2015 12:03:14 -0500 Received: from mailpolicy-01.live.igb.homer.key-systems.net (mailpolicy-01.live.igb.homer.key-systems.net [192.168.1.26]) by mailgw-01.dd24.net (Postfix) with ESMTP id 12DF05FD60 for ; Fri, 27 Nov 2015 17:03:13 +0000 (UTC) Received: from mailgw-01.dd24.net ([192.168.1.35]) by mailpolicy-01.live.igb.homer.key-systems.net (mailpolicy-01.live.igb.homer.key-systems.net [192.168.1.25]) (amavisd-new, port 10235) with ESMTP id Z4Tx1kVk82wJ for ; Fri, 27 Nov 2015 17:03:11 +0000 (UTC) Received: from heisenberg.fritz.box (ppp-93-104-122-99.dynamic.mnet-online.de [93.104.122.99]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mailgw-01.dd24.net (Postfix) with ESMTPSA for ; Fri, 27 Nov 2015 17:03:11 +0000 (UTC) Message-ID: <1448643790.11377.39.camel@scientia.net> Subject: slowness when cp respectively send/receiving on top of dm-crypt From: Christoph Anton Mitterer To: linux-btrfs@vger.kernel.org Date: Fri, 27 Nov 2015 18:03:10 +0100 Content-Type: multipart/signed; micalg="sha-512"; protocol="application/x-pkcs7-signature"; boundary="=-PlyFfuCIi4Plm6Un/x6E" Mime-Version: 1.0 Sender: linux-btrfs-owner@vger.kernel.org List-ID: --=-PlyFfuCIi4Plm6Un/x6E Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Hey. Not sure if that's valuable input for the devs, but here's some vague real-world report about performance: I'm just copying (via send/receive) a large filesystem (~7TB) from on HDD over to another. The devices are both connected via USB3, and each of the btrfs is on top of dm-crypt. It's already obvious that things are slowed down, compared to "normal" circumstances, but from looking at iotop for a while (and the best disk IO measuring tool ever: the LEDs on the USB/SATA bridge) it seems that there are always times when basically no IO happens to disk. There seems to be a repeating schema like this: - First, there is some heavy disk IO (200-250 M/s), mostly on btrfs send and receive processes - Then there are times when send/receive seem to not do anything, but either btrfs-transaction (this I see far less however, and the IO% is far lower, while that of dmcrypt_write is usually to 99%) or dmcrypt_write eat up all IO (I mean the percent value shown in iotop) with now total/actual disk write and read being basically zero during that. Kinda feels as if there would be some large buffer written first, then when that gets full, dm-crypt starts encrypting it during which there is no disk-IO (since it waits for the encryption). Not sure if this is something that could be optimised or maybe it's even a non issue that happens for example while many small files are read/written (the data consists of both, many small files as well as many big files), which may explain why sometimes the actual IO goes up to large >200M/s or at least > 150M/s and sometimes it caps at around 40-80M/s Obviously, since I use dm-crypt and compression on both devices, it may be a CPU issue, but it's a 8 core machine with i7-3612QM CPU @ 2.10GHz... not the fastest, but not the slowest either... and looking at top/htop is happens quite often that there is only very little CPU utilisation, so it doesn't seem as if CPU would be the killing factor here. HTH, Chris. --=-PlyFfuCIi4Plm6Un/x6E Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgMFADCABgkqhkiG9w0BBwEAAKCCEZIw ggW/MIIDp6ADAgECAgMCOakwDQYJKoZIhvcNAQENBQAwVDEUMBIGA1UEChMLQ0FjZXJ0IEluYy4x HjAcBgNVBAsTFWh0dHA6Ly93d3cuQ0FjZXJ0Lm9yZzEcMBoGA1UEAxMTQ0FjZXJ0IENsYXNzIDMg Um9vdDAeFw0xNDA2MTIxNjM2MThaFw0xNjA2MTExNjM2MThaMHwxITAfBgNVBAMTGENocmlzdG9w aCBBbnRvbiBNaXR0ZXJlcjEkMCIGCSqGSIb3DQEJARYVY2FsZXN0eW9Ac2NpZW50aWEubmV0MTEw LwYJKoZIhvcNAQkBFiJtYWlsQGNocmlzdG9waC5hbnRvbi5taXR0ZXJlci5uYW1lMIIBIjANBgkq hkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA4phP/j9vT9dZT+k3ffHxvRWMOuzBnu5O3Fl4y2+WL7pL rfLiEhWzGXhHvjSqpt4vCNSdqy43453nnu8+hMb+uEtqSIL1AHU5eLhuDNVN9S4bt9E7nA2WKYBU LCUi/xCD/GL7ToyJNwhrhzcCZ7pXSc3xVqFoC4f6weU9ExhoEZQNRpTM0BFCOi4fRxvKFNnUYgjK hqy0Ta5H0Xx86mAp0Q4dxoD7mhI5iTF6TRkUheELxF24JCuAf04M89Cwft6DRH1FpJ3yvgW2B5U5 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