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From: Matheus Tavares <>
Subject: Re: RFC: auto-enabling parallel-checkout on NFS
Date: Thu, 19 Nov 2020 01:01:17 -0300	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

Hi, Jeff

On Mon, Nov 16, 2020 at 12:19 PM Jeff Hostetler <> wrote:
> I can't really speak to NFS performance, but I have to wonder if there's
> not something else affecting the results -- 4 and/or 8 core results are
> better than 16+ results in some columns.  And we get diminishing returns
> after ~16.

Yeah, that's a good point. I'm not sure yet what's causing the
diminishing returns, but Geert and I are investigating. Maybe we are
hitting some limit for parallelism in this scenario.

> I'm wondering if during these test runs, you were IO vs CPU bound and if
> VM was a problem.

I would say we are more IO bound during these tests. While a sequential
linux-v5.8 checkout usually uses 100% of one core in my laptop's SSD,
in this setup, it only used 5% to 10%. And even with 64 workers (on a
single core), CPU usage stays around 60% most of the time.

About memory, the peak PSS was around 1.75GB, with 64 workers, and the
machine has 10GB of RAM. But are there other numbers that I should keep
an eye on while running the test?

> I'm wondering if setting thread affinity would help here.

Hmm, I only had one core online during the benchmark, so I think thread
affinity wouldn't impact the runtime.


  reply	other threads:[~2020-11-19  4:02 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-15 19:43 RFC: auto-enabling parallel-checkout on NFS Matheus Tavares
2020-11-16 15:19 ` Jeff Hostetler
2020-11-19  4:01   ` Matheus Tavares [this message]
2020-11-19 14:04     ` Jeff Hostetler
2020-11-20 12:10       ` Ævar Arnfjörð Bjarmason
2020-11-23 23:18       ` Geert Jansen
2020-11-19  9:01 ` Ævar Arnfjörð Bjarmason
2020-11-19 14:11   ` Jeff Hostetler
2020-11-23 23:37   ` Geert Jansen
2020-11-24 12:58     ` Ævar Arnfjörð Bjarmason

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