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Comment by zackelan | Hacker News Reader

http://algo.ing.unimo.it/people/paolo/disk_sched/

tl;dr:

> CFQ separates each process's I/O requests into a separate queue, then rotates through the queues trying to divide the available bandwidth as fairly as it can.

> The BFQ I/O scheduler also maintains per-process queues of I/O requests, but it does away with the round-robin approach used by CFQ. Instead, it assigns an "I/O budget" to each process.

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CFQ is best for mechanical hard drives not sure if it is updated for SSDs, deadline and noop seem better for SSD

There's another new IO scheduler for SSDs: Kyber,

https://patchwork.kernel.org/patch/9672023/

anyone do benches say using fio with this vs. the default scheduler?

nvm: http://www.phoronix.com/scan.php?page=article&item=linux-412...

Aiui kyber is designed for providing consistently low latency, e.g. for desktop users. And maybe specific user-facing server workloads? Those benchmarks mostly seem to test throughput, so are not good at showing the intended effect.

You would want to see something that shows 99th percentile latency of individual reads/writes.

yeah i came to that same conclusion. I may need to do my own testing using Fio.

Why is this being downvoted? AFAIK, this is mostly true.

Random OT question: how can you tell when a comment that isn't yours is being downvoted? I've seen comments like yours a few times before, but I can't see the karma on individual posts. Is there a karma threshold for being able to see this (like the 500 karma threshold for being able to downvote)?

You can tell because the font color starts to fade out till you can barely read the text.

Interesting; I'm unable to notice this on the comment being discussed with my current setup (Firefox on Linux)

That's because it was upvoted back to black since then :)

Haha fair enough

wasn't the downvoter, but general statements like that don't include context of workload (i.e. is it a desktop or server, gaming pc, etc.) so different i/o schedulers would be optimal for different scenarios

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