From: Stephen Hemminger <shemminger@vyatta.com>
To: Eric Dumazet <eric.dumazet@gmail.com>,
David Miller <davem@davemloft.net>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] dcache: better name hash function
Date: Tue, 27 Oct 2009 10:35:36 -0700 [thread overview]
Message-ID: <20091027103536.28cf0a0f@nehalam> (raw)
In-Reply-To: <4AE72B91.7040700@gmail.com>
On Tue, 27 Oct 2009 18:19:13 +0100
Eric Dumazet <eric.dumazet@gmail.com> wrote:
> Stephen Hemminger a écrit :
>
> > So Eric's string10 is fastest for special case of fooNNN style names.
> > But probably isn't best for general strings. Orignal function
> > is >20% slower, which is surprising probably because of overhead
> > of 2 shifts and multipy. jenkins and fnv are both 10% slower.
> >
>
>
> jhash() is faster when strings are longer, being able to process 12 bytes per loop.
>
But jhash is not amenable to usage in namei (with partial_name_hash).
name_hash is rarely done on long strings, the average length of a filename
is fairly short (probably leftover Unix legacy). On my system, average
path component length in /usr is 13 characters; therefore jhash has
no big benefit here.
next prev parent reply other threads:[~2009-10-27 17:35 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <9986527.24561256620662709.JavaMail.root@tahiti.vyatta.com>
2009-10-27 5:19 ` [PATCH] dcache: better name hash function Stephen Hemminger
2009-10-27 5:24 ` David Miller
2009-10-27 17:22 ` [PATCH] net: fold network name hash Stephen Hemminger
2009-10-27 18:02 ` Octavian Purdila
2009-10-27 22:04 ` [PATCH] net: fold network name hash (v2) Stephen Hemminger
2009-10-28 6:07 ` Eric Dumazet
2009-10-28 9:28 ` David Miller
2009-10-28 15:57 ` Stephen Hemminger
2009-10-27 6:07 ` [PATCH] dcache: better name hash function Eric Dumazet
2009-10-27 6:50 ` Eric Dumazet
2009-10-27 7:29 ` Eric Dumazet
2009-10-27 17:07 ` Stephen Hemminger
2009-10-27 17:32 ` Linus Torvalds
2009-10-27 23:08 ` Stephen Hemminger
2009-10-27 23:41 ` Linus Torvalds
2009-10-28 0:10 ` Stephen Hemminger
2009-10-28 0:58 ` Linus Torvalds
2009-10-28 1:56 ` Stephen Hemminger
[not found] ` <4AE72B91.7040700@gmail.com>
2009-10-27 17:35 ` Stephen Hemminger [this message]
2009-10-25 19:58 [PATCH next-next-2.6] netdev: better dev_name_hash Octavian Purdila
2009-10-26 4:43 ` Stephen Hemminger
2009-10-26 22:36 ` [PATCH] dcache: better name hash function Stephen Hemminger <shemminger@vyatta.com>, Al Viro
2009-10-27 2:45 ` Eric Dumazet
2009-10-27 3:53 ` Stephen Hemminger
2009-10-27 16:38 ` Rick Jones
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