The asymmetry strongly suggests that the cipher is not the bottleneck in writes. For reads, take into account that hyper-threaded cores can be vastly slower than real ones. I have seen this admittedly only on an Atom CPU so far, but there I had to disable hyperthreading to get reasonable performance. Arno On Mon, Nov 15, 2010 at 03:36:04PM +0300, Igor Novgorodov wrote: > Hello! > I've got a question regarding encryption performance with > XTS mode in dm-crypt, which is too low for what i > get. > > Test system: > - Supermicro X8DTH-6F > - 1 x 4-Core Xeon E5620 with HyperThreading & AES-NI > - 12Gb RAM DDR3 Reg ECC > > Preparation: > # mount -t tmpfs tmpfs -o size=4G /mnt/tmpfs > # dd if=/dev/zero of=/mnt/tmpfs/image > # losetup /dev/loop0 /mnt/tmpfs/image > > AES-XTS-ESSIV:SHA256 + 512bit key > READ: 220 MB/s > WRITE: 79.6 MB/s > > AES-XTS-ESSIV:SHA256 + 256bit key > READ: 259 MB/s > WRITE: 86.6 MB/s > > And with CBC mode we get reasonable read performance (for AES-NI), but > writing is as almost slow as before: > > AES-CBC-ESSIV:SHA256 > READ: 495 MB/s > WRITE: 107 MB/s > > AES-XTS-PLAIN64 > READ: 271 MB/s > WRTITE: 90.2 MB/s > > What is the problem here? > With aes-cbc-plain64 i get ~560Mb read, and another slow write ~110Mb. > > Is that a limitation of a benchmark with loopback devices & tmpfs? > Write speed is very slow, as i want to saturate a very fast RAID > array (24 x 1Tb RAID6), which can deliver up to 800Mb/sec read: > # echo 3 > /proc/sys/vm/drop_caches > # dd if=/dev/sda of=/dev/null bs=1M count=20480 > 20480+0 records in > 20480+0 records out > 21474836480 bytes (21 GB) copied, 27.3376 s, 786 MB/s > > Any suggestions? Why write speed is so low? > And why with XTS i get 50% speed drop, is that normal? > Thank you! > > P.S. > In Windows with Trucrypt internal benchmark i get 1.6Gb/s > AES encryption speed with AES-NI even on low-end Core i5-620. > > > _______________________________________________ > dm-crypt mailing list > dm-crypt@xxxxxxxx > http://www.saout.de/mailman/listinfo/dm-crypt > -- Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email: arno@xxxxxxxxxxx GnuPG: ID: 1E25338F FP: 0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F ---- Cuddly UI's are the manifestation of wishful thinking. -- Dylan Evans If it's in the news, don't worry about it. The very definition of "news" is "something that hardly ever happens." -- Bruce Schneier _______________________________________________ dm-crypt mailing list dm-crypt@xxxxxxxx http://www.saout.de/mailman/listinfo/dm-crypt
