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The Speed of Time

Brendan Gregg

A Cassandra database cluster had switched to Ubuntu and noticed write latency increased by over 30%. Measuring the speed of time Is there already a microbenchmark for os::javaTimeMillis()? I also shared setting the clocksource in my talks and in my 2015 [Linux tunables] post. Microbenchmark os::javaTimeMillis() on both systems.

Speed 103
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The Speed of Time

Brendan Gregg

A Cassandra database cluster had switched to Ubuntu and noticed write latency increased by over 30%. Measuring the speed of time Is there already a microbenchmark for os::javaTimeMillis()? I also shared setting the clocksource in my talks and in my 2015 Linux tunables post. Microbenchmark os::javaTimeMillis() on both systems.

Speed 52
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The Speed of Time

Brendan Gregg

A Cassandra database cluster had switched to Ubuntu and noticed write latency increased by over 30%. Measuring the speed of time Is there already a microbenchmark for os::javaTimeMillis()? I also shared setting the clocksource in my talks and in my 2015 [Linux tunables] post. Microbenchmark os::javaTimeMillis() on both systems.

Speed 40
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USENIX LISA2021 Computing Performance: On the Horizon

Brendan Gregg

## References I've reproduced the talk references below, so you can click on links: - [Gregg 08] Brendan Gregg, “ZFS L2ARC,” [link] Jul 2008 - [Gregg 10] Brendan Gregg, “Visualizations for Performance Analysis (and More),” [link] 2010 - [Greenberg 11] Marc Greenberg, “DDR4: Double the speed, double the latency? Ford, et al., “TCP

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USENIX SREcon APAC 2022: Computing Performance: What's on the Horizon

Brendan Gregg

My personal opinion is that I don't see a widespread need for more capacity given horizontal scaling and servers that can already exceed 1 Tbyte of DRAM; bandwidth is also helpful, but I'd be concerned about the increased latency for adding a hop to more memory. Ford, et al., “TCP

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USENIX LISA2021 Computing Performance: On the Horizon

Brendan Gregg

## References I've reproduced the talk references below, so you can click on links: - [Gregg 08] Brendan Gregg, “ZFS L2ARC,” [link] Jul 2008 - [Gregg 10] Brendan Gregg, “Visualizations for Performance Analysis (and More),” [link] 2010 - [Greenberg 11] Marc Greenberg, “DDR4: Double the speed, double the latency? Ford, et al., “TCP

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SpaceX Spending $10 Billion to Make the Internet 20ms Faster

MachMetrics

Elon Musk’s need for speed. However, there is excitement around Starlink for other reasons – namely, the implications it might have for internet speed and latency – even by just a small amount (20 milliseconds on average). This ultimately guides us to one conclusion: Speed is incredibly important.