linux-kernel - Re: [PATCH 05/15] RDS: increase size of hash-table to 8K

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Message-ID: <560098ED.7@oracle.com>
Date:	Mon, 21 Sep 2015 16:55:25 -0700
From:	santosh shilimkar <santosh.shilimkar@...cle.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	ssantosh@...nel.org
Subject: Re: [PATCH 05/15] RDS: increase size of hash-table to 8K

On 9/21/2015 4:05 PM, David Miller wrote:
> From: Santosh Shilimkar <santosh.shilimkar@...cle.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@...nel.org>
>> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@...cle.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.

OK. Thanks for AF_NETLINK pointer. I will look it up.

Regards,
Santosh
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