netdev - Re: [PATCH] net: unix socket code abuses csum

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Message-Id: <20140304.162329.504474868666088316.davem@davemloft.net>
Date:	Tue, 04 Mar 2014 16:23:29 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	anton@...ba.org, edumazet@...gle.com, gustavold@...ux.vnet.ibm.com,
	netdev@...r.kernel.org
Subject: Re: [PATCH] net: unix socket code abuses csum_partial

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Tue, 04 Mar 2014 10:50:53 -0800

> On Tue, 2014-03-04 at 13:41 -0500, David Miller wrote:
> 
>> Alternatively you could just make unix_hash_fold() use csum_fold(),
>> right?
>> 
>> static inline unsigned int unix_hash_fold(__wsum n)
>> {
>> 	unsigned int hash = (__force unsigned int) csum_fold(n);
>> 
>> 	hash ^= hash>>8;
>> 	return hash&(UNIX_HASH_SIZE-1);
>> }
> 
> Or simply use full_name_hash()

I would prefer not, because this would be a performance regression
on platforms other than x86 and ARM, because only they implement
the optimized load_unaligned_zeropad().

Other architectures would end up with a byte-by-byte hash computation.
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