From owner-freebsd-arch@FreeBSD.ORG Mon May 24 23:55:42 2004 Return-Path: Delivered-To: freebsd-arch@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 302C516A4CE for ; Mon, 24 May 2004 23:55:42 -0700 (PDT) Received: from cs.rice.edu (cs.rice.edu [128.42.1.30]) by mx1.FreeBSD.org (Postfix) with ESMTP id 0E12343D3F for ; Mon, 24 May 2004 23:55:42 -0700 (PDT) (envelope-from alc@cs.rice.edu) Received: from localhost (calypso.cs.rice.edu [128.42.1.127]) by cs.rice.edu (Postfix) with ESMTP id 6F6BB4AA05; Tue, 25 May 2004 01:54:11 -0500 (CDT) Received: from cs.rice.edu ([128.42.1.30]) by localhost (calypso.cs.rice.edu [128.42.1.127]) (amavisd-new, port 10024) with LMTP id 02786-01-87; Tue, 25 May 2004 01:54:11 -0500 (CDT) Received: by cs.rice.edu (Postfix, from userid 19572) id 1A73E4A9F2; Tue, 25 May 2004 01:54:11 -0500 (CDT) Date: Tue, 25 May 2004 01:54:10 -0500 From: Alan Cox To: dillon@backplane.com, arch@freebsd.org Message-ID: <20040525065410.GA23877@cs.rice.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.3.28i X-Virus-Scanned: by amavis-20030616-p7 at cs.rice.edu Subject: Re: Network Stack Locking X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 25 May 2004 06:55:42 -0000 >:Sounds a lot like a lot of the Mach IPC optimizations, including their use >:of continuations during IPC to avoid a full context switch. >: >:Robert N M Watson FreeBSD Core Team, TrustedBSD Projects >:robert@fledge.watson.org Senior Research Scientist, McAfee Research > > Well, I like the performance aspects of a continuation mechanism, but > I really dislike the memory overhead. Even a minimal stack is > expensive when you multiply it by potentially hundreds of thousands > of 'blocking' entities such as PCBs.. say, a TCP output stream. > Because of this the overhead and cache pollution generated by the > continuation mechanism increases as system load increases rather > then decreases. When the explicit continuation mechanism was used, the thread's stack was freed when the thread blocked and a new stack allocated when the thread was restarted. Here is a URL: http://citeseer.ist.psu.edu/draves91using.html. Notice the mention of space reduction in the abstract. It's worth reading. Alan