Date: Sun, 18 Dec 2011 11:52:42 +0400 From: Andrey Chernov <ache@FreeBSD.ORG> To: Ian Smith <smithi@nimnet.asn.au> Cc: Bruce Cran <bruce@cran.org.uk>, Ivan Klymenko <fidaj@ukr.net>, Doug Barton <dougb@FreeBSD.ORG>, freebsd-stable@FreeBSD.ORG, "O. Hartmann" <ohartman@mail.zedat.fu-berlin.de>, Current FreeBSD <freebsd-current@FreeBSD.ORG>, freebsd-performance@FreeBSD.ORG Subject: Re: SCHED_ULE should not be the default Message-ID: <20111218075241.GA45367@vniz.net> In-Reply-To: <20111218164924.L64681@sola.nimnet.asn.au> 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>
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On Sun, Dec 18, 2011 at 05:51:47PM +1100, Ian Smith wrote: > On Sun, 18 Dec 2011 02:37:52 +0000, Bruce Cran wrote: > > On 13/12/2011 09:00, Andrey Chernov wrote: > > > I observe ULE interactivity slowness even on single core machine (Pentium > > > 4) in very visible places, like 'ps ax' output stucks in the middle by ~1 > > > second. When I switch back to SHED_4BSD, all slowness is gone. > > > > I'm also seeing problems with ULE on a dual-socket quad-core Xeon machine > > with 16 logical CPUs. If I run "tar xf somefile.tar" and "make -j16 > > buildworld" then logging into another console can take several seconds. > > Sometimes even the "Password:" prompt can take a couple of seconds to appear > > after typing my username. > > I'd resigned myself to expecting this sort of behaviour as 'normal' on > my single core 1133MHz PIII-M. As a reproducable data point, running > 'dd if=/dev/random of=/dev/null' in one konsole, specifically to heat > the CPU while testing my manual fan control script, hogs it up pretty > much while regularly running the script below in another konsole to > check values - which often gets stuck half way, occasionally pausing > _twice_ before finishing. Switching back to the first konsole (on > another desktop) to kill the dd can also take a couple/few seconds. This issue not about slow machine under load, because the same slow machine under exact the same load, but with SCHED_4BSD is very fast to response interactively. I think we should not misinterpret interactivity with speed. I see no big speed (i.e. compilation time) differences, switching schedulers, but see big _interactivity_ difference. ULE in general tends to underestimate interactive processes in favour of background ones. It perhaps helps to compilation, but looks like slowpoke OS from the interactive user experience. -- http://ache.vniz.net/
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