Re: [PATCH 05/15] RDS: increase size of hash-table to 8K
From: santosh shilimkar
Date: Mon Sep 21 2015 - 11:52:29 EST
On 9/21/2015 1:31 AM, David Laight wrote:
From: Santosh Shilimkar
Sent: 20 September 2015 00:05
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 significant 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.
Can't you use of on the dynamically sizing hash tables?
8k hash table entries is OTT for a lot of systems.
Do you know an example in Linux kernel uses that ? What I
certainly don't want is over-head of re-sizing whenever
that happens in running systems running multiple databases.
Memory is certainly not an issue on the systems where RDS
has been deployed. I certainly don't want to over-use the
memory but in the system where RDS being used and also
amount of connection it needs to handle, it needs
bigger bucket.
Regards,
Santosh
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