netdev - RE: [PATCH 05/15] RDS: increase size of hash-table to 8K

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Date:	Mon, 21 Sep 2015 08:31:23 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'Santosh Shilimkar' <santosh.shilimkar@...cle.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"ssantosh@...nel.org" <ssantosh@...nel.org>
Subject: RE: [PATCH 05/15] RDS: increase size of hash-table to 8K

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 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.

Can't you use of on the dynamically sizing hash tables?
8k hash table entries is OTT for a lot of systems.

	David

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