From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.saout.de ([127.0.0.1]) by localhost (mail.saout.de [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 3QZCZdA-DXyk for ; Sun, 22 Jul 2012 23:55:43 +0200 (CEST) Received: from mail1.merlins.org (magic.merlins.org [209.81.13.136]) (using TLSv1.2 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.saout.de (Postfix) with ESMTPS for ; Sun, 22 Jul 2012 23:55:43 +0200 (CEST) Date: Sun, 22 Jul 2012 14:55:39 -0700 From: Marc MERLIN Message-ID: <20120722215539.GB12951@merlins.org> References: <20120722190757.GB10089@merlins.org> <20120722202213.GA7306@fancy-poultry.org> <20120722190757.GB10089@merlins.org> <1342986452.26887.3.camel@scapa> <20120722203929.GB3925@merlins.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120722203929.GB3925@merlins.org> Subject: Re: [dm-crypt] aes-xts-plain with aes_x86_64 makes my SSD 5x slower than my encrypted HD List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Yves-Alexis Perez , dm-crypt@saout.de, htd@fancy-poultry.org On Sun, Jul 22, 2012 at 01:39:29PM -0700, Marc MERLIN wrote: > Result is the same: > gandalfthegreat:~# hdparm -tT /dev/mapper/ssdcrypt > > /dev/mapper/ssdcrypt: > Timing cached reads: 16614 MB in 2.00 seconds = 8317.50 MB/sec > Timing buffered disk reads: 68 MB in 3.08 seconds = 22.09 MB/sec > > Grumble. > > It shouldn't be a hardware problem since I do see 400MB/s before encryption. Ok, I'm not sure I understand. I mounted /dev/mapper/ssdcrypt (btrfs) and when going through the filesystem I get much higher speeds than using dd on the raw block device. But... when I run The test below shows that I can access the encrypted SSD 10x faster by talking to it through a btrfs filesystem than doing a dd read from the device node. So I suppose I could just ignore the dd device node thing, however not really. Let's take a directory with some source files inside: gandalfthegreat:/var/local# find src | wc -l 15261 gandalfthegreat:/var/local# echo 3 > /proc/sys/vm/drop_caches; time du -sh src 514M src real 0m5.865s So on an encrypted spinning disk, it takes 6 seconds. On my SSD in the same machine with the same encryption and the same btrfs filesystem, I get 5 times slower: gandalfthegreat:/mnt/btrfs_pool1/var/local# time du -sh src 514M src real 0m24.937s Incidently 5x is also the speed difference between my encrypted HD and encrypted SSD with dd. Now, why du is 5x slower and dd of a file from the filesystem is 2.5x faster, I have no idea :-/ See below: 1) drop caches gandalfthegreat:/mnt/btrfs_pool1/var/local/VirtualBox VMs/w2k_virtual# echo 3 > /proc/sys/vm/drop_caches gandalfthegreat:/mnt/btrfs_pool1/var/local/VirtualBox VMs/w2k_virtual# dd if=w2k-s001.vmdk of=/dev/null 2146631680 bytes (2.1 GB) copied, 8.03898 s, 267 MB/s -> 267MB/s reading from the file through the encrypted filesystem. That's good. For comparison gandalfthegreat:/mnt/mnt2# dd if=w2k-s001.vmdk of=/dev/null 2146631680 bytes (2.1 GB) copied, 4.33393 s, 495 MB/s -> almost 500MB/s reading through another unencrypted filesystem on the same SSD gandalfthegreat:/mnt/btrfs_pool1/var/local/VirtualBox VMs/w2k_virtual# dd if=/dev/mapper/ssdcrypt of=/dev/null bs=1M count=1000 1048576000 bytes (1.0 GB) copied, 45.1234 s, 23.2 MB/s -> 23MB/s reading from the block device that my FS is mounted from. WTF? gandalfthegreat:/mnt/btrfs_pool1/var/local/VirtualBox VMs/w2k_virtual# echo 3 > /proc/sys/vm/drop_caches; dd if=w2k-s001.vmdk of=test 2146631680 bytes (2.1 GB) copied, 17.9129 s, 120 MB/s -> 120MB/s copying a file from the SSD to itself. That's not bad. gandalfthegreat:/mnt/btrfs_pool1/var/local/VirtualBox VMs/w2k_virtual# echo 3 > /proc/sys/vm/drop_caches; dd if=test of=/dev/null 2146631680 bytes (2.1 GB) copied, 8.4907 s, 253 MB/s -> reading the new copied file still shows 253MB/s, good. gandalfthegreat:/mnt/btrfs_pool1/var/local/VirtualBox VMs/w2k_virtual# dd if=test of=/dev/null 2146631680 bytes (2.1 GB) copied, 2.11001 s, 1.0 GB/s -> reading without dropping the cache shows 1GB/s I'm very lost now, any idea what's going on? Thanks, Marc -- "A mouse is a device used to point at the xterm you want to type in" - A.S.R. Microsoft is to operating systems .... .... what McDonalds is to gourmet cooking Home page: http://marc.merlins.org/