Date: Fri, 12 Mar 2004 13:28:18 +0300 From: "Artem Koutchine" <matrix@itlegion.ru> To: <freebsd-hardware@freebsd.org> Subject: Multiprocessor system VS one processor system Message-ID: <002f01c4081c$bd720810$0c00a8c0@artem> References: <CD1C1AC62C4DA944914E36E7B3DD904313DB17@sestosrv004p.ad.octapharma.se>
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Hi! I need to understand something very clear. As I understand FreeBSD (as of 4.9) runs one process per one CPU. This means, that if i have dual systems with 500Mhz CPUs one process can never run faster than on a single 500Mhz CPU. However, if i substitute those two CPUs with one 1000Mhz, that one process will run twice as fast than on dual 500Mhz, however, to box will become a bit less responsive, because in a dual box when one CPU is loaded, another one may have some spare time to respond. However, in case of very loaded box both CPUs a extremely loaded and the box will be as responsive as single 1000Mhz CPU box 100% loaded. So, according to what i just said there is not real reason to setup a dual CPU box under FREEBSD unless you want to have 5000Mhz box, but there is no CPU with such speed, so you put two 2500Mhz CPU in it and if you are running a lot of processes with short run periods you will get overal perfomance somewhere near 5000Mhz. However, when i subsituted two 500Mhz CPUs with 1500Mhz one (even with less 2nd level cache) on a heavy loaded web server i notice that sites started to load faster. So, it seems as one 3X Mhz CPU is faster that two X MHz CPUs, at least for web server with sql base and many perl scripts. So, there are two questions: 1) Am I right or am wrong? 2) Does FreeBSD 5.X run one process only on one CPU or it can run on thread of a process on one CPU and another thread on another CPU? Regards, Artem
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