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Date: Fri, 31 Jul 2009 16:40:01 +0200 From: Andi Kleen <andi@...stfloor.org> To: "Zhang, Yanmin" <yanmin_zhang@...ux.intel.com> Cc: Robert Hancock <hancockrwd@...il.com>, Corrado Zoccolo <czoccolo@...il.com>, LKML <linux-kernel@...r.kernel.org>, linux-acpi@...r.kernel.org, venkatesh.pallipadi@...el.com Subject: Re: Dynamic configure max_cstate Andreas Mohr <andi@...as.de> writes: > Instead we should strive for a far-reaching _generic_ mechanism > which gathers average latencies of various I/O activities/devices > and then uses some formula to determine the maximum (not necessarily ACPI) > idle latency that we're willing to endure (e.g. average device I/O reply latency > divided by 10 or so). The interrupt heuristics in the menu cpuidle governour are already attempting this, based on interrupt rates (or rather wakeup rates) which are supposed to roughly correspond with IO rates and scheduling events together. Apparently that doesn't work in this case. The challenge would be to find out why and improve the menu algorithm to deal with it. I doubt a completely new mechanism is needed or makes sense. > And in addition to this, we should also take into account (read: skip) > any idle states which kill busmaster DMA completely > (in case of busmaster DMA I/O activities, that is) This is already done. -Andi -- ak@...ux.intel.com -- Speaking for myself only. -- 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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