Date: Thu, 14 Jun 2007 13:27:01 +0200 From: Thomas Vogt <thomas@bsdunix.ch> To: NOC Meganet <tec@mega.net.br> Cc: freebsd-performance@freebsd.org Subject: Re: PAPI in the ports Message-ID: <46712605.5090907@bsdunix.ch> In-Reply-To: <200706140806.05674.tec@mega.net.br> References: <d825e0270706140152j6012592ah18beef95942bb051@mail.gmail.com> <4671118D.1040404@bsdunix.ch> <200706140806.05674.tec@mega.net.br>
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Hi NOC Meganet wrote: > On Thursday 14 June 2007 06:59:41 Thomas Vogt wrote: >> Hi >> >> Thats sounds nice. You wrote "The goal of the PmcTools project is to >> provide FreeBSD's developers and system administrators with >> non-intrusive, low-overhead and innovative ways of measuring and >> analysing system performance" your website. Have you ever measured the >> performance impact of such tools? >> >> I'm interested to run such tool on production machines in the future but >> only if the performance impact isn't that high. >> > > Hi > ... even if the tool (whatever it is) does not require much system resources > it triggers processes in order to measure their or the system's performance. > So long as you do not push the system to or over the edge you might not get > valuable numbers. So I mean, any performance measuring does or must stress > the system. That is at least my understanding. So probably running > performance tests on a production server is not the very best idea. Yes you're right. But to have a such feature on a production system is nice if you have to debug issues. If I get a problem I can easily debug it without to simulate everything in the lab. It's not that I want to run such features 24/7. But perhaps "options HWPMC_HOOKS" in the kernel enables some hooks which could cause performance penalties even if I don't actively use such feature very often. Like many other debug options in the kernel. I don't know. Regards, Tom
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