Date: Tue, 16 Dec 2008 10:10:38 -0700 (MST) From: "M. Warner Losh" <imp@bsdimp.com> To: scottl@samsco.org 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 Message-ID: <20081216.101038.1172765453.imp@bsdimp.com> In-Reply-To: <4947D474.9040802@samsco.org> References: <200812161604.mBGG4fBd041647@svn.freebsd.org> <4947D474.9040802@samsco.org>
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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
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