On 07/24/2012 07:57 AM, Marc MERLIN wrote: > Mmmh, so I installed "standard" linux-image-3.2.0-3-amd64 from debian. > And.... > nothing changed :( Well. I found SSD where I can reproduce something similar. Seems page cache messes something with readahead... # lsblk /dev/sdc -t NAME ALIGNMENT MIN-IO OPT-IO PHY-SEC LOG-SEC ROTA SCHED RQ-SIZE sdc 0 512 0 512 512 0 noop 128 └─sdc_null_crypt (dm-0) 0 512 0 512 512 0 128 - Disable readahead # blockdev --setra 0 /dev/mapper/sdc_null_crypt # hdparm -t /dev/mapper/sdc_null_crypt Timing buffered disk reads: 106 MB in 3.01 seconds = 35.18 MB/sec (pretty bad) But with direct-io it still works: # hdparm --direct -t /dev/mapper/sdc_null_crypt Timing O_DIRECT disk reads: 698 MB in 3.00 seconds = 232.44 MB/sec (now with read-ahead set to 4M) # blockdev --setra 8192 /dev/mapper/sdc_null_crypt # hdparm -t /dev/mapper/sdc_null_crypt Timing buffered disk reads: 664 MB in 3.00 seconds = 221.29 MB/sec So. Can you please try to increase readahead (and also run it with direct-io)? Just to check if it is the same problem or not... Thanks, Milan _______________________________________________ dm-crypt mailing list dm-crypt@xxxxxxxx http://www.saout.de/mailman/listinfo/dm-crypt
