Re: splice methods in character device driver

From: Jens Axboe
Date: Tue Jun 16 2009 - 14:28:22 EST

On Tue, Jun 16 2009, Steve Rottinger wrote:
> >> I'm doing about 300MB/s to my hardware RAID, running two instances of my
> >> splice() copy application
> >> (One on each RAID channel). I would like to combine the two RAID
> >> channels using a software RAID 0;
> >> however, splice, even from /dev/zero runs horribly slow to a software
> >> RAID device. I'd be curious
> >> to know if anyone else has tried this?
> >>
> >
> > Did you trace it and find out why it was slow? It should not be. Moving
> > 300MB/sec should not be making any machine sweat.
> >
> I haven't dug into this too deeply, yet; however, I did discover
> something interesting: The splice runs much faster using the software
> raid, if I transfer to a file on a mounted filesystem, instead of the
> raw md block device.

OK, that's a least a starting point. I'll try this tomorrow (raw block
device vs fs file).

Jens Axboe

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