cycbuff rawpartition, linux performance
Miquel van Smoorenburg
list-inn-workers at news.cistron.nl
Fri Feb 18 10:19:59 UTC 2000
In article <cistron.Pine.LNX.4.21.0002171206330.7927-100000 at micro.internexus.net>,
Laszlo Vecsey <master at internexus.net> wrote:
>I remember reading that on linux, doing a cycbuff with a raw partition is
>not faster for some reason or another..
It would be much faster if it were possible but it isn't.
>perhaps related to mmap or the
>buffer cache in the kernel. Faster than creating a file on a regular
>partition that is, and using that as the cycbuff.
Well Linux doesn't support mmap() on block devices, and the CNFS
code needs that so you have to use regular files.
>So keeping the 2gig limits in mind, is it better/worse to use raw
>partitions now or individual files sitting on the partition?
>I'm using the 2.2.x production kernels, and guessing that things have
>in 2.3.x experimental.. but not worth switching over to :)
No, in 2.3.x you still can't use mmap() on a block device. Perhaps
that will be fixed before 2.4, perhaps it won't.
However there is a workaround - rawfs. That is a filesystem that
shows the partitions on your disk as files. As files in a filesystem
_can_ be mmap()ed, this is the solution.
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