Date: Mon, 11 Dec 2006 07:58:39 -0800 From: <soralx@cydem.org> To: <freebsd-chat@freebsd.org> Subject: Re: Venting my frustration with FreeBSD Message-ID: <20061211075839.11bc0900@freen0de> In-Reply-To: <200612061805.05727.jhb@freebsd.org> References: <200612041443.15154.josh@tcbug.org> <200612061006.56852.jhb@freebsd.org> <20061206134536.0c775367@freen0de> <200612061805.05727.jhb@freebsd.org>
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> > > 512-way machine? Scaling on a 512-way machine is quite a > > > different ball of wax from scaling on 4-way, and scaling up to 32 > > > and 64 is going to be another ball of wax as well. > > can you give a few examples how scaling ability can be a function of > > the number of cores? seems like my curiosity exceeds my imagination > > today -- can't come up with any good reasons why this is true :) > > You may make different tradeoffs. For example, on a 4-cpu system, it > may be fine to have certain data structures shared across CPUs and > protected via a lock which avoids the overhead of multiple copies and > complexity of updating multiple copies of a data structure. However, > with a 512-way system you may have to resort to using duplicated > per-cpu (or maybe per-cpu group) copies of a structure because the > tradeoffs are different. Well, I see what you mean. However, as for this example, it should be possible to always share data between CPU groups (that can be sized dynamically), right? Thus, given an optimal dynamics algorithm, performance would always be close to best possible? More generally, it seems that some code may often be added to make the scaling ability more or less independent of the quantity of processing units. I still believe that an operating system that scales close to linearly is possible. The question is, how big an overhaul FreeBSD needs for a jump start to becoming of interest in the areas where performance & scalability matter? > -- > John Baldwin [SorAlx] ridin' VN1500-B2
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