On Wed, 4 Jun 2014, Doug Anderson wrote: > As we saw in (clocksource: exynos_mct: cache mct upper count), the > time spent reading the MCT shows up fairly high in real-world > profiles. That means that it's worth some optimization. > > We get a roughly 10% speedup in userspace gettimeofday() by using an > ldmia to read the two halfs of the MCT. That seems like a worthwhile > thing to do. > > Before: 1173084 us for 1000000 gettimeofday in userspace > After: 1045674 us for 1000000 gettimeofday in userspace > > NOTE: we could actually do better than this if we really wanted to. > Technically we could register the clocksource as a 32-bit timer and > only use the "lower" half. Doing so brings us down to 1014429 us for > 1000000 gettimeofday in userspace (and doesn't even require assembly > code). That would be an alternative to this change. I was about to ask exactly that question: What's the advantage of the 64 bit dance there? AFAICT nothing. Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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