linux-kernel - Re: [PATCH RESEND][pciutils] libpci: pci_id_lookup

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Message-ID: <mj+md-20131215.091609.28546.nikam@ucw.cz>
Date:	Sun, 15 Dec 2013 10:18:39 +0100
From:	Martin Mares <mj@....cz>
To:	Kay Sievers <kay@...y.org>
Cc:	Tom Gundersen <teg@...m.no>, LKML <linux-kernel@...r.kernel.org>,
	linux-pci@...r.kernel.org
Subject: Re: [PATCH RESEND][pciutils] libpci: pci_id_lookup - add udev/hwdb
 support

Hello Kay,

> Libpci and its linear search through megabytes of text files for evey
> new query is too inefficient, that we cannot afford to use it during
> early bootup. It was the largest hit left in bootup profiling on
> machines booting userspace in the sub-1-second range on common
> machines. It was probably never meant to provide efficient queries,
> but it's the reason we can never use it during early boot.

I do not know what you are speaking about -- libpci definitely does
not perform linear scans on pci.ids. It builds a hash table from pci.ids
on the first query and and all subsequent queries are O(1) on average.

				Martin
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