Date: Sun, 18 Dec 2011 02:34:39 -0800 From: Adrian Chadd <adrian@freebsd.org> To: Alexander Best <arundel@freebsd.org> Cc: Bruce Cran <bruce@cran.org.uk>, Ivan Klymenko <fidaj@ukr.net>, Doug Barton <dougb@freebsd.org>, Ian Smith <smithi@nimnet.asn.au>, "O. Hartmann" <ohartman@mail.zedat.fu-berlin.de>, Current FreeBSD <freebsd-current@freebsd.org>, freebsd-stable@freebsd.org, freebsd-performance@freebsd.org Subject: Re: SCHED_ULE should not be the default Message-ID: <CAJ-VmomJ9D63xYyg4udKu1FnihVworgp8MrxzXwpG2XVZww8DA@mail.gmail.com> In-Reply-To: <20111218102600.GA44118@freebsd.org> References: <4EE1EAFE.3070408@m5p.com> <4EE22421.9060707@gmail.com> <4EE6060D.5060201@mail.zedat.fu-berlin.de> <4EE69C5A.3090005@FreeBSD.org> <20111213104048.40f3e3de@nonamehost.> <20111213090051.GA3339@vniz.net> <4EED5200.20302@cran.org.uk> <20111218164924.L64681@sola.nimnet.asn.au> <20111218075241.GA45367@vniz.net> <20111218102401.GA42627@freebsd.org> <20111218102600.GA44118@freebsd.org>
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The trouble is that there's lots of anecdotal evidence, but noone's really gone digging deep into _their_ example of why it's broken. The developers who know this stuff don't see anything wrong. That hints to me it may be something a little more creepy - as an example, the interplay between netisr/swi/taskqueue/callbacks and such. It may be that something is being starved that isn't obviously obvious. It's just a stab in the dark, but it sounds somewhat plausible based on what I've seen ULE do in my network throughput hacking. I applaud reppie for trying to make it as easy as possible for people to use KTR to provide scheduler traces for him to go digging with, so please, if you have these issues and you can absolutely reproduce them, please follow his instructions and work with him to get him what he needs. Adrian (wow, lots of personal pronouns packed into one sentence. It must be sleep time.)
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