Date: Mon, 30 May 2005 20:30:26 -0600 (MDT) From: "M. Warner Losh" <imp@bsdimp.com> To: bde@zeta.org.au Cc: rwatson@FreeBSD.org, daniel_k_eriksson@telia.com, freebsd-arch@FreeBSD.org Subject: Re: MPSAFE CAM? Message-ID: <20050530.203026.35855612.imp@bsdimp.com> In-Reply-To: <20050531113008.R91505@delplex.bde.org> References: <20050530.102803.74664036.imp@bsdimp.com> <20050530182650.R90885@fledge.watson.org> <20050531113008.R91505@delplex.bde.org>
next in thread | previous in thread | raw e-mail | index | archive | help
In message: <20050531113008.R91505@delplex.bde.org>
Bruce Evans <bde@zeta.org.au> writes:
: On Mon, 30 May 2005, Robert Watson wrote:
:
: > On Mon, 30 May 2005, M. Warner Losh wrote:
: >
: >> In message: <20050529121224.L52379@fledge.watson.org>
: >> Robert Watson <rwatson@FreeBSD.org> writes:
: >> : driver, we've gained many of the benefits of making MPSAFE. Especially
: >> if
: >> : we can knock Giant off a lot of the remaining non-CAM device drivers that
: >> : it's still stuck over.
: >>
: >> usb, psm and atkbd are important ones for interactive performance...
: >
: > And the tty subsystem becomes an immediate dependency for several of these.
:
: Interactive performance is irrelevant here. You can can lose efficiency
: by competing for Giant a few hundred thousand times in the time that
: it takes an interactive user to notice. The problem is that non-interactive
: performance is impaired by using Giant locking anywhere. Using it for
: interactive devices is only a problem if the interaction often requires
: holding Giant for a long time. It doesn't for most input devices
: including keyboards, but it might for slow bulk output devices like
: syscons consoles.
Also in the case of usb, it means that all devices sharing interrupts
with the usb bridges are effectively under giant...
Warner
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20050530.203026.35855612.imp>