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Date: Sun, 29 Jun 2008 13:34:18 +0200 From: Martin Sustrik <sustrik@...tmq.com> To: David Newall <davidn@...idnewall.com> CC: Martin Lucina <mato@...elna.sk>, linux-kernel@...r.kernel.org Subject: Re: Higher than expected disk write(2) latency David Newall wrote: > Martin Lucina wrote: >> Measurement of the write(2) time is performed using the TSC, so any >> latency there is negligible. > > Measuring each write is lavish and bound to impact the results. To > measure sustained throughput, get the time only at start and end, and > divide the difference by the number of writes. Hi, We're using RDTSC to measure time, which takes ~30 nanoseconds to complete. I would say this is negligible given that latency of a write is 5 orders of magnitude higher. Martin -- 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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