Date: Sat, 21 Jan 2012 10:18:42 +0100 From: Martin Sugioarto <martin@sugioarto.com> To: FreeBSD Stable Mailing List <freebsd-stable@freebsd.org> Cc: Joe Holden <lists@rewt.org.uk> Subject: Re: Timekeeping in stable/9 Message-ID: <20120121101842.786fc402@zelda.sugioarto.com> In-Reply-To: <20120118075049.289954e8@zelda.sugioarto.com> References: <4F15D643.8000907@rewt.org.uk> <20120118075049.289954e8@zelda.sugioarto.com>
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--Sig_/fvjL7IS5lNjXtKav3XSMwtD Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable Am Wed, 18 Jan 2012 07:50:49 +0100 schrieb Martin Sugioarto <martin@sugioarto.com>: > I can confirm this on VirtualBox. I've been running WinXP inside > VirtualBox and measured network I/O during downloads. It showed me > very high download rates (around 800kB/s) while it's physically > possible to download 200kB/s through DSL here (Germany sucks with > DSL, even in largest cities, btw!). >=20 > I correlated this behavior with high disk I/O on the host. That means > that the timer issues on the virtual host appear when I start a > larger cp job on the host. I also immediately thought that this has > something to do with timers. Hi everybody, I just want to add some information on this. I tested a few things with VirtualBox yesterday. I switched off ntpd on the host and tested if there are differences, but the clock is working correctly on the host. I tested it a few times, it is stable, as I expect it to be. It seems to be rather a software problem with VirtualBox. I can see that when the host is under heavy load (CPU!) the guest does not get enough runtime to adjust the clock correctly. After a few minutes there has been a difference of 50 seconds between the host and guest clock. And furthermore, I don't quite understand how the real time clock works in VirtualBox but it seems to slide in the different directions causing weird results with progress bars on MS-Windows XP. I just want to explain why I thought that I/O influences this. I have got my hard disk encrypted, so it puts some load on the CPU, too. If you want to test VirtualBox behavior, you can simple dd from /dev/random and look at the weird results in VirtualBox. -- I hope it helps further, Martin --Sig_/fvjL7IS5lNjXtKav3XSMwtD Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.18 (FreeBSD) iQIcBAEBAgAGBQJPGoL3AAoJEF8wvLx/5p/7yQcQAKCBJdpgIOetIxeKSIm2RZPS sQ/lfpgmbQYAhlFnxq+WWE6mCpOYDVubyA1NV9uZIk/vgKl3gDNxyfYrLYUKvGW9 N6X1uK7dorfGlOijRnO2lmjC4L9wCf5eYLgC1nWX/wcBNdItWAv3BI0O+BM4+hIT 4vGMVLHCc2AvAjvKkaQmhcqbB0+0McfPRB5Jx7E5XDyn7Mse8OYkJICahyki/kYF Z1a91z4sl4EyYq9ZoOm8ByuyAqUVFuqMne2CvNRwuVISWHsjHCUum9BVHBgtVpzV nz3tAWEKonswAyHquqFHQTy6Msitmxk0Nunjf7yT382xyI5TWWaoFGZiPkg7KMoF 5wyOGO+KI8DboWiI+X6qMibHRa1NTL6ok6Dx9SQwmmIER+CI+IYVusD5VyyvUC4c 0FRVd0aid1mMXJZcnHEw5BGFDtKvJvhuxUkAGS4WNG7inuhi20fetTUHbPeEfRKC j0Tb5x6yu2lcvfShG9DEUVmzwgfM/TXd6exM0zPl4OuGtnpJNSPRtBIJoCUrT9qn 4gt3ggQj1LneYHNAREi03LjQ4l5+DO4RwXcvuXQHemOEQQfwLsNJS+SICjpgmCeQ yYdfGzMIl7qF7tUpogfTJjghTkVEYFBgdCZY4LLes9MtT8DW2p0SI339+yqBM0Hj UziuIiuXiX0LLwxBAUaV =1BA7 -----END PGP SIGNATURE----- --Sig_/fvjL7IS5lNjXtKav3XSMwtD--
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