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Date:      Sat, 21 Sep 2013 12:53:36 -0700
From:      Adrian Chadd <adrian@freebsd.org>
To:        Vincent Schut <schut@sarvision.nl>
Cc:        FreeBSD Questions <freebsd-questions@freebsd.org>
Subject:   Re: this 48-core box...
Message-ID:  <CAJ-VmonDO3rbbctx-m3HF=7_m2EfjVh0n=yaM4=FhJdOtXnK8w@mail.gmail.com>
In-Reply-To: <20130920110535.42c984da@sarvision.nl>
References:  <52388C9B.6030205@foxbatcapital.com> <20130919155327.115e7344@sarvision.nl> <alpine.BSF.2.00.1309191157410.56073@btw.pki2.com> <20130920110535.42c984da@sarvision.nl>

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.. just as a data point - there was a thread a while ago about numeric
processing performance on linux vs bsd.

It all boiled down to how jemalloc versus the linux allocator(s) allocate
blocks. jemalloc will page align things after a certain size. Linux didn't.
So when doing numeric processing, there was a lot of cache aliasing going
on leading to inefficient cache usage and redundant memory operations.

When the same workload on Linux was run on FreeBSD but with the Linux
library/allocators, the performance was identical.

No-one followed through. I think I may have to write a blog post about it.


-adrian



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