From mboxrd@z Thu Jan 1 00:00:00 1970 MIME-Version: 1.0 In-Reply-To: <49AE073B.3070501@orcasystems.com> References: <086f4496e85bfab0a28a5c19dad17554@quanstro.net> <49AE073B.3070501@orcasystems.com> Date: Wed, 4 Mar 2009 00:05:54 -0500 Message-ID: <3aaafc130903032105i742648d2o86ccd2630c4aa61c@mail.gmail.com> From: "J.R. Mauro" To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Subject: Re: [9fans] threads vs forks Topicbox-Message-UUID: af2aa7ba-ead4-11e9-9d60-3106f5b1d025 On Tue, Mar 3, 2009 at 11:44 PM, James Tomaschke wr= ote: > erik quanstrom wrote: >>> >>> I think the reason why you didn't see parallelism come out earlier in t= he >>> PC market was because they needed to create new mechanisms for I/O. =A0= AMD did >>> this with Hypertransport, and I've seen 32-core (8-socket) systems with >>> this. =A0Now Intel has their own I/O rethink out there. >> >> i think what you're saying is equivalent to saying >> (in terms i understand) that memory bandwidth was >> so bad that a second processor couldn't do much work. > > Yes bandwidth and latency. >> >> but i haven't found this to be the case. =A0even the >> highly constrained pentium 4 gets some milage out of >> hyperthreading for the tests i've run. >> >> the intel 5000-series still use a fsb. =A0and they seem to >> scale well from 1 to 4 cores. > > Many of the circuit simulators I use fall flat on their face after 4 core= s, > say. =A0However I blame this on their algorithm not hardware. > > I wasn't making an AMD vs Intel comment, just that AMD had created HTX al= ong > with their K8 platform to address scalability concerns with I/O. > >> are there benchmarks that show otherwise similar >> hypertransport systems trouncing intel in multithreaded >> performance? =A0i don't recall seeing anything more than >> a moderate (15-20%) advantage. > > I don't have a 16-core Intel system to compare with, but: > http://en.wikipedia.org/wiki/List_of_device_bandwidths#Computer_buses > > I think the reason why Intel developed their Common Systems Interconnect > (now called QuickPath Interconnect) was to address it's shortcomings. > > Both AMD and Intel are looking at I/O because it is and will be a limitin= g > factor when scaling to higher core counts. And soon hard disk latencies are really going to start hurting (they already are hurting some, I'm sure), and I'm not convinced of the viability of SSDs. There was an interesting article I came across that compared the latencies of accessing a register, a CPU cache, main memory, and disk, which put them in human terms. As much as we like to say we understand the difference between a millisecond and a nanosecond, seeing cache access expressed in terms of moments and a disk access in terms of years was rather illuminating, if only to me. Same article also put a google search at only slightly slower latency than hard disk access. The internet really is becoming the computer, I suppose. > >> >> - erik >> >> > > >