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To: scottl@samsco.org
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Cc: svn-src-head@FreeBSD.org, mav@FreeBSD.org, src-committers@FreeBSD.org,
	svn-src-all@FreeBSD.org
Subject: Re: svn commit: r186182 - head/sys/dev/ata
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In message: <4947D474.9040802@samsco.org>
            Scott Long <scottl@samsco.org> writes:
: Alexander Motin wrote:
: > Author: mav
: > Date: Tue Dec 16 16:04:40 2008
: > New Revision: 186182
: > URL: http://svn.freebsd.org/changeset/base/186182
: > 
: > Log:
: >   Call ata_legacy() only once on attach and save it's result. Scanning PCI
: >   configuration registers (which are not going to change) on every interrupt
: >   looks expensive, especially when interrupt is shared. Profiling shows me 3%
: >   of time spent by atapci0 on pure network load due to IRQ sharing with em0.
: > 
: 
: Nice change.  PCI Config registers are exceptionally slow to access on 
: most systems.

And we've been recommending to people for years that they avoid config
space access in interrupt handlers.  Maybe it is time for something
that checks and prints a warning?

Warner