Re: [libre-riscv-dev] spinlocks considered harmful

From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
To: Libre-RISCV General Development <libre-riscv-dev@lists.libre-riscv.org>
Subject: Re: [libre-riscv-dev] spinlocks considered harmful
Date: Sat, 9 May 2020 08:51:48 +0100
Message-ID: <CAPweEDw8wNEQbpZ1Gv1-M2iQyR6K=DS+kJLsY5vXBEYSUPROww@mail.gmail.com> (raw)
In-Reply-To: <CAC2bXD5L6ZK-Vmb5b2C8X2=BcecybqFkFWjpNWcuMB=utuuNXw@mail.gmail.com>

On Sat, May 9, 2020 at 12:20 AM Jacob Lifshay <programmerjake@gmail.com> wrote:

> I ended up reporting a bug to PyO3 to not use spinlocks, the explanatory
> blog post I liked to is quite informative and I'd consider it recommended
> reading for anyone writing multi-threaded programs and/or using atomics:
>
> https://matklad.github.io/2020/01/02/spinlocks-considered-harmful.html

oh look.  they're rediscovering systems programming and fundamental
systems design, because they're working in a high-level language and
haven't had the kind of training and experience that this extremely
well written article describes.

remember, jacob, i was one of the key architects on samba, which had
people working on it who absolutely had to know what they were doing.

HP told us back in 1997 that they were running 48,000 simultaneous
users across 19 separate HP/UX mini computers, each with NFS-mounts
onto 4 mainframes.  so - remember this is on hardware from *1997* -
they had 3,000 simultaneous users per HP/UX minicomputer *and*
capacity to spare to do outgoing NFS traffic.

if samba had been designed using spinlocks for resource contention it
would have tanked at around 150-200 users per minicomputer.

l.

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