Date: Thu, 15 Feb 2001 16:41:47 -0700 (MST) From: Nate Williams <nate@yogotech.com> To: Terry Lambert <tlambert@primenet.com> Cc: seth@pengar.com (Seth Leigh), nate@yogotech.com (Nate Williams), freebsd-smp@FreeBSD.ORG Subject: Re: possible problem with SMP? Message-ID: <14988.26939.53659.399934@nomad.yogotech.com> In-Reply-To: <200102152336.QAA09980@usr08.primenet.com> References: <5.0.2.1.0.20010215020051.01b9fc70@hobbiton.shire.net> <200102152336.QAA09980@usr08.primenet.com>
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> In effect, both these models are a call-conversion model, where you > exchange a blocking call for a non-blocking call (or a block on an > LWP, and the creation of a new LWP to continue running), plus a > thread context switch. > > Neither of these models improves concurrency on a UP system. Sure they do. Not in all cases, but in most cases they do ipmrove concurrency since they're allowing other threads to execute while a non-threaded application would block on that system call. It does not scale as well on a UP system like SA's do, but in many case the threading model is more effecient 'most of the time' vs. a multi-process model. > Threaded applications will block on resource unavailability; it's > really irrelevent whether this happens in the kernel or in user > space. Except the cost of 'switching context' in userland is much lower than in the kernel. (As you said, this is the what 'Lightweight' implies with LWP's. :) Nate To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-smp" in the body of the message
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