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Message-Id: <20090810121444.974476902@de.ibm.com> Date: Mon, 10 Aug 2009 14:14:44 +0200 From: Martin Schwidefsky <schwidefsky@...ibm.com> To: linux-kernel@...r.kernel.org Cc: Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>, john stultz <johnstul@...ibm.com> Subject: [RFC][patch 0/1] nohz delay performance optimization Greetings, I'm still working on the cpu idle/wakeup path to improve the performance of some ping-pong workloads. This patch is the latest idea and proved rather effective. The idea is that the timer tick is not switched off if the cpu did some work in the last tick period. This will add an unnecessary tick interrupt if the cpu goes truly idle but will save some cycles for the nohz reprogramming if the cpu wakes up again for more work. Currently the patch only works on s390, the arch_needs_cpu() will be true if there has been any other interrupt than timer interrupts in the last tick period. I think this could be improved with an explicit call to request a nohz delay. The call should be added to selective points in the code, e.g. whenever a process != idle is scheduled, whenever a bottom half is run, and so on. Comments? -- blue skies, Martin. "Reality continues to ruin my life." - Calvin. -- 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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