> > i also think that your examples don't translate well into the
> > plan 9 world. we trade performance for keeping ramfs out of
> > the kernel, etc. (620mb/s on my much slower machine, btw.)
>
> This is for dd </dev/zero >/dev/null? What do you get for
> various block sizes?
that's for dd -if /dev/zero -of /n/testramfs/bigfile -bs 128k -count
`{aux/number 100m/128k}
the block size won't matter much, since ramfs will get 8k writes
no matter what.
> If you are getting 620MBps that means you will definitely not
> exceed that number for disk based filesystems.
wrong-o!
when i first started testing the myricom 10gbe in 2006, i was able
to get 470MB/s from an sr with the aoe driver with no caching
or readahead on the plan 9 side. by today's standards, those were
very slow systems.
i don't have the time to set up this test rig right now, but i think
it's safe to assume that we can pound this performance with modern
hardware and a modern aoe appliance.
but even with 470ms/s from the disk, with memory caching and
ken fs's good performance (no context switches, no tlb flushes),
it's safe to assume that we can already beat 620mb/s from the
file server.
what you're seeing is the fact that ramfs is just plain slow.
- erik
