Date: Tue, 29 Oct 2002 13:06:36 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: Terry Lambert <tlambert2@mindspring.com> Cc: Raymond Kohler <raymond.j.kohler@lmco.com>, current@FreeBSD.ORG Subject: Re: questions about the state of current Message-ID: <200210292106.g9TL6aoc010659@apollo.backplane.com> References: <2570443.1035916854787.JavaMail.wshttp@emss03g01.ems.lmco.com> <3DBEF55E.A0F9ED1B@mindspring.com>
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:Most of the speed difference is WITNESS, INVARIANTS, and other :debugging code that's turned on by default in the config files :for -current. You can turn most of it off. That said, -current :is slower than -stable in a number of places, so expect some :slowdown, if you are running non-concurrent code. I would concur with this diagnosis. With witness turned off -current is around 15% slower then -stable for general purpose computing, like a 'make buildworld -j 20', and I expect that -stable will beat out -current on single-cpu boxes for a long time to come. That said, it should be noted that nearly all the really cool development projects are only happening in -current. Things like KSEs, hardware crypto support, UFS2, and so forth, only exist in -current. Very little of this work is going to be MFC'd so depending on your needs -current could very well end up faster. And, of course, there is the fact that computing power seems to double every year. Since -current's overhead is in large part due to mutexes and other concurrency mechanisms, and these are literally pure-cpu mechanisms rather then memory or I/O dependant, decisions should be based on capability rather then something as insignificant as a 15% performance difference between the 'rough cut' -current and the well aged -stable. In coming years concurrency is going to become the leading performance-improving mechanism for computers. -Matt To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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