Hi,
I have done some nfs/rdma tests and found impressive transfer
rates, but only when the file data is in cache. On the other hand,
using straight nfs over ipoib I am able to get decent transfer
rates one first read (not cached) when I tweak:
echo 128 > /proc/fs/nfsd/pool_threads
echo 1024 > /sys/block/sd?/queue/nr_requests
echo 16384 > /sys/block/sd?/queue/read_ahead_kb (or using blockdev
with 8192)
My question: Does the nfs/rdma setup bypass the readahead
mechanism in the kernel?
If it does,
1) this may account for the major difference described above,
2) explain why transfers are _very_ fast only on the second go
around--because it is in cached (assuming it fits in the cache)
For both cases, I am using a 2.6.26 bigmem kernel with the necessary
tweaks.
Thanks,
John
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