Date: Mon, 11 Mar 2013 16:07:40 -0700 From: Matthew Jacob <mjacob@freebsd.org> To: freebsd-arch@freebsd.org Subject: Re: Unmapped buffers: to be merged in several days Message-ID: <513E63BC.9020105@freebsd.org> In-Reply-To: <CAJP=Hc9V9HVpdevD3=Qgk812CYwbmc-Q4HgtPyupb7zTfmTB6g@mail.gmail.com> References: <20130311091852.GR3794@kib.kiev.ua> <86k3pe1cl3.fsf@ds4.des.no> <20130311182454.GX3794@kib.kiev.ua> <329178079.20130312010425@serebryakov.spb.ru> <20130311211158.GE3794@kib.kiev.ua> <CAJP=Hc9V9HVpdevD3=Qgk812CYwbmc-Q4HgtPyupb7zTfmTB6g@mail.gmail.com>
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On 3/11/2013 3:22 PM, Jim Harris wrote: > On Mon, Mar 11, 2013 at 2:11 PM, Konstantin Belousov <kostikbel@gmail.com>wrote: > >> FWIW, I tried to get an Intel documentation for IOAT engine which should >> allow to perform the XOR checksumming of the unmapped buffers, suitable >> for e.g. hardware-assisted software raid5, but did not succeeded. >> > Please note that XOR checksumming support only exists in the > E5-1600/2400/2600/4600 series (Sandy Bridge Xeon) and C5500/C3500 series > (Jasper Forest - based on Nehalem Xeon) processors. The SNB Xeon series > It's been our experience at Xyratex that the h/w XOR checksum engine is generally slower than the CPU, at least with more modern Sandy Bridge chipsets. But, as you know, YMMV.
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