On Mon, Jul 16 2007, David Brown wrote: > On 7/14/07, David Brown <[EMAIL PROTECTED]> wrote: >> I was forced to put full (almost) hard drive encryption on my laptop >> so that all the Open Source Work I get paid to do will be protected in >> case someone tries to steal it and so they won't find any personal >> information about me if they get a hold of my laptop (because every >> idiot keeps their entire life history on their computers). >> >> Besides the futility of the above statement I've been noticing some >> oddities with how linux and dm-crypt handles I/O on the system. >> >> Now normally I get about 30Mb/s write speed I would expect some sort >> of drop in performance due to the encryption but currently I'm getting >> about 9Mb/s write speed and I'm kinda confused as to what the choke >> point is and how to improve the write speed, if it can be. >> >> Currently both my swap and root are encrypted with the default debian >> installer encryption and there's two kcryptd processes running. Now >> from what I've noticed when I'm dumping data to disk they both seem to >> be working, yet I'm not swapping or anything. So am I right to assume >> that the two kcryptd processes are running in parallel encrypting the >> data to the one root device? Also they only seem to be using 20% of >> the processors they are running on, why isn't it 100%? I'm guessing >> that the data isn't being either compressed or blown up when >> encrypting using this encryption style (but I'm not an expert). Would >> making more kcryptd threads increase the I/O speed (more processes >> doing encrypting)? Is there a way to specify more threads of kcryptd? >> >> I'm kinda at a loss, so any help would be appreciated. >> - David Brown >> > > I should remember never to email the LKML during the weekend... > > Did anyone see this? > > I did some number crunching and with about 15Mb/s read and 9Mb/s write > I end up copying files on the hard drive locally at about 3Mb/s > (rounded). Which is really lame getting twice without encryption was > much better. > > I'm using the ata_piix driver in the 2.6.22.1 kernel.
Try and blktrace the crypt device, perhaps? Do a simple dd from your crypted device to /dev/null, and run blktrace on the device at the same time. Just for a few seconds. Then check with blkparse if anything obvious pops up. -- Jens Axboe - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
