Date: Tue, 25 Feb 1997 20:18:42 +1100 From: Bruce Evans <bde@zeta.org.au> To: bde@zeta.org.au, msmith@atrad.adelaide.edu.au Cc: freebsd-hardware@freebsd.org, ken@stox.pr.mcs.net Subject: Re: Memory speed of P6-200 (256k) Message-ID: <199702250918.UAA03535@godzilla.zeta.org.au>
index | next in thread | raw e-mail
>> Er, no, fast copying reduces buffer cache overheads. Buffer cache >> overheads are almost large enough to significantly reduce the advantages >> of busmastering DMA over (slow) PIO. > >ie. the fast copyin/out code will make busmaster devices faster too? 8) Yes, that was the original motivation for speeding up copyout() and copyin(). Satoshi had lots of disk bandwidth (40MB/sec?) from multiple controllers but couldn't use it all because copying alone was limited to 40MB/sec. He speeded it up to 70+MB/sec on a P5-Triton system by using the FPU, and I speeded it up a few more MB/sec by fine tuning. The dd speeds are almost twice as large since the input buffer is small enough to stay in the P5's L1 data cache. Brucehome | help
Want to link to this message? Use this
URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199702250918.UAA03535>