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Date: Sat, 6 Sep 2008 11:30:21 -0700 From: "Ulrich Drepper" <drepper@...il.com> To: "Arjan van de Ven" <arjan@...radead.org> Cc: "Phil Endecott" <phil_wueww_endecott@...zphil.org>, "Linux Kernel Mailing List" <linux-kernel@...r.kernel.org> Subject: Re: nice and hyperthreading on atom On Sat, Sep 6, 2008 at 9:42 AM, Arjan van de Ven <arjan@...radead.org> wrote: > As an OS one COULD decide to just not schedule the nice task at all, > but then, especially on atom where HT has a high efficiency, your cpu > is mostly idle ... One thread being idle is even on Atom the right thing to do in some situations. If you have processes which, when HT is used, experience high pressure on the common cache(s) then you should not schedule them together. We can theoretically find out whether this is the case using the PMCs. With perfmon2 hopefully on the horizon soon it might actually be possible to automatically make these measurements. There is another aspect I talked to Peter about already. We really want concurrent threat scheduling in some cases. For the implementation of helper threads you don't want two threads to be scheduled independently, you want them to be scheduled on a HT pair. Currently this isn't possible except by pinning them to fixed threads. We really want to have a new way to express this type of scheduling (Peter, how did you call it?) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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