Not logged in
Log in now
Create an account
Subscribe to LWN
LWN.net Weekly Edition for May 16, 2013
A look at the PyPy 2.0 release
PostgreSQL 9.3 beta: Federated databases and more
LWN.net Weekly Edition for May 9, 2013
(Nearly) full tickless operation in 3.10
A hash-based DOS attack on Btrfs
Posted Dec 14, 2012 2:54 UTC (Fri) by cyanit (guest, #86671)
However, if other instructions can be scheduled by the out-of-order CPU in the meantime, then AES should be much faster, since the reciprocal throughput is actually 10 cycles on Sandy Bridge and should only take up one execution unit.
Without AES instructions things are most likely reversed.
Posted Dec 14, 2012 11:23 UTC (Fri) by daniel (subscriber, #3181)
Posted Dec 14, 2012 15:27 UTC (Fri) by drag (subscriber, #31333)
Posted Dec 15, 2012 2:11 UTC (Sat) by daniel (subscriber, #3181)
The most important result here is not the inappropriateness of CRC as a hash, but that Btrfs is a complex beast, still in development, a critical bug was just exposed, and likely a few more remain. Given wide enough testing and continued developer commitment it will become stable, but today it is not. From where I sit, it looks like Ext4 will be wearing its standard Linux filesystem crown for some time yet.
Posted Dec 15, 2012 6:17 UTC (Sat) by SEJeff (subscriber, #51588)
Posted Dec 15, 2012 13:18 UTC (Sat) by vonbrand (subscriber, #4458)
From a cursory look over, I'd say 220 *minutes* isn't just a bad hash degenerating to a linear search...
Posted Dec 15, 2012 2:46 UTC (Sat) by wahern (subscriber, #37304)
Copyright © 2013, Eklektix, Inc.
Comments and public postings are copyrighted by their creators.
Linux is a registered trademark of Linus Torvalds