Date: Thu, 16 Oct 2008 13:06:18 +0300 From: Alexander Motin <mav@FreeBSD.org> To: Stanislav Sedov <stas@freebsd.org> Cc: freebsd-arm@freebsd.org, zbeeble@gmail.com, freebsd-mobile@freebsd.org, freebsd-current@freebsd.org Subject: Re: RFC: PCI SD host controller driver & mmc/mmcsd modules improvements Message-ID: <48F7121A.2010307@FreeBSD.org> In-Reply-To: <1224123783.00025735.1224113402@10.7.7.3> References: <1223284984.00022179.1223272802@10.7.7.3> <1223497390.00023332.1223487003@10.7.7.3> <1223832181.00024566.1223819402@10.7.7.3> <1223929384.00025003.1223917802@10.7.7.3> <1224112991.00025726.1224102602@10.7.7.3> <1224123783.00025735.1224113402@10.7.7.3>
next in thread | previous in thread | raw e-mail | index | archive | help
Stanislav Sedov wrote: > On Wed, 15 Oct 2008 23:25:11 +0300 > Alexander Motin <mav@FreeBSD.org> mentioned: >> Completely fortunate I have noticed that number of iterations depends on >> my laptop power source. After small investigation I have found that it >> actually depends on dev.cpu.0.freq value. With default value 2400 I have >> only several iterations. But every double frequency decrease doubles >> iteration count. With minimum value 100MHz I have more then 100 >> iterations. Same time it doesn't looks like this time is a real wall >> time. It looks like DELAY() used in a loop has some problems with time >> counting. > > What do you mean? DELAY(9) on your laptop doesn't correspond to the > real time? Yes. It works fine when laptop operates at full frequency, but proportionally reduces time interval when powerd drops frequency down. I have also evidence about the same problem on another laptop with 7.1-PRERELEASE. > AFAIK, DELAY(9) relies on current timecounter for time > accountiong, so there might be problems with it. Have you tried > switching the kern.timecounter.hardware sysctl to see if it will > affect results? It was late and I am not very aware in FreeBSD time counting, so I have not tried to investigate it deeper. -- Alexander Motin
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?48F7121A.2010307>