Date: Fri, 20 Jan 2006 04:52:15 -0500 From: Kris Kennaway <kris@obsecurity.org> To: Scott Long <scottl@samsco.org> Cc: current@freebsd.org, Gleb Smirnoff <glebius@freebsd.org>, Julian Elischer <julian@elischer.org>, Kris Kennaway <kris@obsecurity.org> Subject: Re: kernel thread as real threads.. Message-ID: <20060120095214.GA11088@xor.obsecurity.org> In-Reply-To: <43D0AB26.5070407@samsco.org> References: <43D05151.5070409@elischer.org> <20060120030105.GA5286@xor.obsecurity.org> <43D0715A.7020302@elischer.org> <20060120061955.GA8687@xor.obsecurity.org> <20060120085226.GQ83922@FreeBSD.org> <43D0AB26.5070407@samsco.org>
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[-- Attachment #1 --] On Fri, Jan 20, 2006 at 02:19:34AM -0700, Scott Long wrote: > Gleb Smirnoff wrote: > > >On Fri, Jan 20, 2006 at 01:19:55AM -0500, Kris Kennaway wrote: > >K> > the example I showed was the 'ps' from ddb which of course doesn't > >show K> > any stats anyhow. > >K> > >K> Yeah, I know that, but they're also not displayed in ps(1) or top(1), > >K> etc. > > > >And this is a serious issue, that is present in our last releases. If a > >was a newbie installing FreeBSD for first time, this fact will hurt my > >impression about operating system most. > > > > For KSE, threads are just a figment of the imagination of the kernel. A > thread that > the kernel sees has no specific correlation to a thread that exists in > an application. > Trying to associate stats with these threads is absolultely meaningless. > The > processing time accumulated for a particular thread that the kernel sees > could well > be the aggregate of a number of user threads, and those user threads are > likely migrating > between the kernel threads. That's the whole point of M:N threading > =-) Saying that > thread 1 did X amount of work and thread 2 did Y amount of work simply > has no meaning, > other than that the parent process did X+Y amount of work. Correct me if I'm wrong, but the stats aren't accounted to the parent process either. I'm pretty sure I've seen situations where a thread was using a lot of CPU, but if you believe top(1) then every process in the system is idle (except for the fact that the system is 0% idle). In this situation there's no way to tell which threaded process is using resources. Kris [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.2 (FreeBSD) iD8DBQFD0LLOWry0BWjoQKURAuIwAJ9pBRtJkEMSX4Qu+ItEc+Ciaf7N7wCePhm/ C2btEc7vjioDM+6sqjoMNhw= =xfCy -----END PGP SIGNATURE-----
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