On 18 Apr 2001 18:31:02 -0700, Andy Arvai wrote:
>
> I was looking at my system log file at the output from the raid drivers
> and I noticed the following:
>
> raid0 personality registered
> raid1 personality registered
> raid5 personality registered
> raid5: measuring checksumming speed
> 8regs : 1342.400 MB/sec
> 32regs : 906.400 MB/sec
> pIII_sse : 1990.800 MB/sec
> pII_mmx : 2214.000 MB/sec
> p5_mmx : 2354.000 MB/sec
> raid5: using function: pIII_sse (1990.800 MB/sec)
> md driver 0.90.0 MAX_MD_DEVS=256, MD_SB_DISKS=27
> md.c: sizeof(mdp_super_t) = 4096
>
> Why does the driver choose pIII_sse vs. the faster p5_mmx?
I'm beginning to think about putting this in the RAID FAQ (which I've
been lax about lately, sorry). The reason it uses the PIII stuff
instead of others is that it takes advantage of the SSE instruction sets
in the CPU, and as such, uses significantly less CPU cycles to get the
same work done. So while the absolute bandwidth that it can handle may
be less, it's probably a better choice, as it leaves more of the CPU to
do real work.
Greg
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