On a second thought, do you think we still need one rwlock per hash chain ?
>
TCP established hash table entries: 1048576 (order: 12, 16777216 bytes)
On this x86_64 machine, we 'waste' 8 MB of ram for those rwlocks.
With RCU, we touch these rwlocks only on TCP connection
creation/deletion, maybe we could reduce to one rwlock or a hashed array
of 2^N rwlocks (2^N depending on NR_CPUS), like in net/ipv4/route.c ?
TCP connection/deletion can be a rather frequent occurance. Web servers
and all, even with persistent connections. Contention there would
show-up in a SPECweb benchmark just as an example. SPECweb is a bit
involved - especially SPECweb2005. The netperf TCP_CRR or TCP_CC test
could be used - likely aggregates of them - to measure things, but it
might take more than a small CPU count system to see contention going to
a "too small" number of locks.
I suspect that one rwlock would be too small :) Hashed locks might work
- would it introduce more cache misses?
rick jones
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