kern/178467: [request] Optimized Checksum Code for ZFS

[Steven Hartland]

The following reply was made to PR kern/178467; it has been noted by GNATS.

From: "Steven Hartland" <smh at freebsd.org>
To: <bug-followup at freebsd.org>,
	<jkeller at bbiinternational.com>
Cc:  
Subject: Re: kern/178467: [request] Optimized Checksum Code for ZFS
Date: Fri, 10 May 2013 09:47:59 +0100

 We would need something more to go no than "looks like" I'm afraid.
 
 Also Fletcher4 is the default checksum which achieves ~4GB/s
 per core in hashing performance, where as SHA-256 even with
 hand written assembly manages less than 1/10th that performance,
 so if your looking for performance for checksums use the
 default Fletcher4 instead of the SHA-256.
 
 That said new processors do have HW support which could be
 used to accelerate SHA-256 support, details of this can be
 found here:-
 http://download.intel.com/embedded/processor/whitepaper/327457.pdf
 
 These sorts of core feature enhancements should be discussed
 and implemented upstream at illumos.
 
     Regards
     Steve