linux-kernel - Re: [PATCH] dev: use ifindex hash for dev_seq

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Message-ID: <20111017081205.2e41d03f@nehalam.linuxnetplumber.net>
Date:	Mon, 17 Oct 2011 08:12:05 -0700
From:	Stephen Hemminger <shemminger@...tta.com>
To:	Daniel Baluta <dbaluta@...acom.com>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	Mihai Maruseac <mihai.maruseac@...il.com>, davem@...emloft.net,
	mirq-linux@...e.qmqm.pl, therbert@...gle.com, jpirko@...hat.com,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Mihai Maruseac <mmaruseac@...acom.com>
Subject: Re: [PATCH] dev: use ifindex hash for dev_seq_ops

On Mon, 17 Oct 2011 11:03:54 +0300
Daniel Baluta <dbaluta@...acom.com> wrote:

> > This assumes device ifindexes are contained in a small range
> > [N .. N + X]
> >
> > I understand this can help some benchmarks, but in real world this wont
> > help that much once ifindexes are 'fragmented' (If really this multi
> > thousand devices stuff is for real)
> >
> > Listen, we currently have 256 slots in the hash table.
> >
> > Can we try to make 'offset' something like  (slot_number<<24) +
> > (position in hash chain [slot_number]), instead of (position in devices
> > global list)
> 
> 
> Eric, we can refine the idea of our first patch [1], where we recorded
> the (bucket, offset) pair. Stephen, do you agree with this?
> 
> 
> thanks,
> Daniel.
> 
> [1] http://patchwork.ozlabs.org/patch/118331/

Using buckets is fine, my idea about ifindex was just to try and
preserve the order, but it doesn't matter.
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