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

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Date:	Mon, 17 Oct 2011 11:03:54 +0300
From:	Daniel Baluta <dbaluta@...acom.com>
To:	Eric Dumazet <eric.dumazet@...il.com>, shemminger@...tta.com
Cc:	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

> 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/
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