From mboxrd@z Thu Jan 1 00:00:00 1970 MIME-Version: 1.0 In-Reply-To: References: <20090708084855.GA1371@polynum.com> <8ea4f24e3b6cd8f73321c0d62b295ccb@hamnavoe.com> <439ce9144800e42fe15a33950bcb15e6@coraid.com> <13426df10907081052p1a4ab07mfb3331fcff8b2d4c@mail.gmail.com> Date: Wed, 8 Jul 2009 15:40:14 -0400 Message-ID: <9ab217670907081240x43703ca5x1240e8296db94d3c@mail.gmail.com> From: "Devon H. O'Dell" To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [9fans] Google finally announces their lightweight OS Topicbox-Message-UUID: 16ead104-ead5-11e9-9d60-3106f5b1d025 2009/7/8 erik quanstrom : >> But don't underestimate the value of the interesting ideas in the >> linux kernel that get the performance, e.g. RCU. I don't think there >> are any OSes that have scaled to 4096 CPUs at this point besides >> Linux. > > i thought that massively parallel harvard-arch machines had > generally fallen out of favor in favor of blue gene-style hardware. > > is this incorrect? I think it depends on the application. I have a friend who studies fluid dynamics for scramjets and he was mentioning how doing some of those calculations requires ultra-low latency. The algorithms they need to use require multiple passes, and each calculation is affected by surrounding `blocks.' With infiniband and whatnot, this might be moot (he's doing his stuff on 32-core systems right now, so it's not even to that degree), but perhaps there are still applications that still significantly benefit from that architecture. They are quite the opposite of `embarrassingly parallel' problems (a la distributed.net / SETI / Folding). That said, I have no idea what the performance / latency characteristics are of a system with 32 cores and 32 CPUs connected with infiniband / some other proprietary high speed interconnect, or what that would look like performance-wise if it was scaled to 4096 cores versus quad-CPU boards with interconnects. > - erik -dho