From owner-cvs-all  Wed Jun 27 14:34: 6 2001
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Date: Wed, 27 Jun 2001 16:33:45 -0500
From: Jonathan Lemon Alfred Perlstein <bright@sneakerz.org>
To: Doug Rabson <dfr@nlsystems.com>
Cc: Matt Dillon <dillon@earth.backplane.com>,
	John Baldwin <jhb@FreeBSD.org>,
	"Brian F. Feldman" <green@FreeBSD.org>,
	Mike Silbersack <silby@FreeBSD.org>, cvs-committers@FreeBSD.org,
	cvs-all@FreeBSD.org, jlemon@FreeBSD.org, bmilekic@FreeBSD.org
Subject: Re: cvs commit: src/sys/netinet tcp_input.c tcp_output.c tcp_sub
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References: <200106271537.f5RFbIQ40573@earth.backplane.com> <Pine.BSF.4.33.0106272128380.96893-100000@herring.nlsystems.com>
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In-Reply-To: <Pine.BSF.4.33.0106272128380.96893-100000@herring.nlsystems.com>; from dfr@nlsystems.com on Wed, Jun 27, 2001 at 09:38:12PM +0100
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* Doug Rabson <dfr@nlsystems.com> [010627 15:39] wrote:
> 
> Since we don't have sufficient lock pushdown to get any significant part
> of the kernel outside the scope of Giant, any implementation of
> lightweight ithreads would not make a noticeable performance improvement
> because it will be contending on Giant too often. This same problem tends
> to double the number of context switches in our existing implementation
> which is a major performance issue.
> 
> In the long run, we need to implement lightweight ithreads but until we
> can get a significant fraction of the kernel out from under Giant,
> performance is not going to improve.

Well for the most part the network drivers should be mpsafe, since
mbuf and ifq queues are protected by locks we should be able to
get them out from under giant.

-Alfred

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