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

[Jason Keller]

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

From: Jason Keller <jkeller at bbiinternational.com>
To: Steven Hartland <smh at freebsd.org>, "bug-followup at freebsd.org"
	<bug-followup at freebsd.org>
Cc:  
Subject: RE: kern/178467: [request] Optimized Checksum Code for ZFS
Date: Fri, 10 May 2013 13:21:26 +0000

 Ok, thank you Steven - I'll gather up more detailed information when I have=
  my test environment fully fleshed out so I have absolute apples to apples =
 numbers and can fully constrain my testing to one hardware platform (the pl=
 atforms were slightly different, same processors and memory though).  I'll =
 file that as an RFE with Illumos if that's what you think is best.  I just =
 wanted to put that out there, since I certainly noticed the difference in m=
 y many weeks of testing different platforms here (OmniOS, Solaris 11.0, Sol=
 aris 11.1, FreeBSD 9.1, Nexenta 4 CE).  Didn't really know where I should f=
 ile that particular RFE, so I figured I'd start with the kernel team.  I di=
 dn't think that the SHA256 implementation in FreeBSD was taken exactly from=
  Illumos.
 
 JASON KELLER, CCNA | IT MANAGER | BBI INTERNATIONAL
 
 B: +1 701 738 4910 | :: +1 701 426 6240 | :: jkeller at bbiinternational.com
 j: Mon-Thu 0730-1130 & 1230-1700 UTC-5 and Fri 0730-1000 UTC-5
 Like the job I did?  Recommend me on LinkedIn > =20
 
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 -----Original Message-----
 From: Steven Hartland [mailto:smh at freebsd.org]=20
 Sent: Friday, May 10, 2013 3:48 AM
 To: bug-followup at freebsd.org; Jason Keller
 Subject: Re: kern/178467: [request] Optimized Checksum Code for ZFS
 
 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 ha=
 shing 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 accelera=
 te SHA-256 support, details of this can be found here:- http://download.int=
 el.com/embedded/processor/whitepaper/327457.pdf
 
 These sorts of core feature enhancements should be discussed and implemente=
 d upstream at illumos.
 
     Regards
     Steve