Date: Fri, 20 Sep 1996 21:29:42 -0700 (PDT) From: asami@freebsd.org (Satoshi Asami) To: michaelv@MindBender.serv.net Cc: freebsd-scsi@freebsd.org, freebsd-current@freebsd.org, freebsd-isp@freebsd.org Subject: Re: Streamlogic RAID array benchmarks Message-ID: <199609210429.VAA14425@silvia.HIP.Berkeley.EDU> In-Reply-To: <199609210411.VAA20862@MindBender.serv.net> (michaelv@MindBender.serv.net)
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* >Yeah, it's a P5 (133MHz). We got pretty much the same result with the
* >P6 (200MHz) too (which is kinda surprising, given that their memory
* >system is so much slower).
*
* How is that surprising? The SCSI controller lives on the other side
* of the bus, and does the bus-mastering irrespective of the CPU. The
* CPU does not do bcopies for bus-mastering SCSI transfers.
It does, because this is a bufferred I/O. We were measuring this
through the filesystem, remember?
An interesting sidenote of this is that when we were using the same
P5-133 with the regular (rep/movsl) copyin/copyout, we got only about
20MB/s. We changed it to the Pentium-optimized copy, and managed to
push it up close to 30MB/s.
The slow bcopy can move about 40MB/s, the fast one 80MB/s. However,
the P6-200, despite its 45MB/s bcopy speed, gives us the same 30MB/s
through the filesystem.
(For those you like math, 45MB/s is 22.2ns/byte, and 30MB/s is 33.3ns/B,
and given that the max transfer rate on of 33MHz PCI is 132MB/s, or
7.5 ns/B, this is really close to the limit (22.2 + 7.5 = 29.7 =~
33.3)....)
Satoshi
P.S. Doing parallel reads from raw devices, I could get about 65MB/s
on the P5...haven't tried that on the P6.
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