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SubjectRe: [PATCH 05/15] RDS: increase size of hash-table to 8K
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From: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Date: Sat, 19 Sep 2015 19:04:42 -0400

> Even with per bucket locking scheme, in a massive parallel
> system with active rds sockets which could be in excess of multiple
> of 10K, rds_bin_lookup() workload is siginificant because of smaller
> hashtable size.
>
> With some tests, it was found that we get modest but still nice
> reduction in rds_bind_lookup with bigger bucket.
>
> Hashtable Baseline(1k) Delta
> 2048: 8.28% -2.45%
> 4096: 8.28% -4.60%
> 8192: 8.28% -6.46%
> 16384: 8.28% -6.75%
>
> Based on the data, we set 8K as the bind hash-table size.
>
> Signed-off-by: Santosh Shilimkar <ssantosh@kernel.org>
> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>

Like others I would strongly prefer that you use a dynamically sized
hash table.

Eating 8k just because a module just happened to get loaded is really
not appropriate.

And there are many other places that use such a scheme, one example is
the AF_NETLINK socket hash table.


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