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From: Patrick Oppenlander <patrick.oppenlander@gmail.com>
To: musl@lists.openwall.com
Subject: Re: Some questions
Date: Mon, 30 Apr 2018 13:55:16 +1000	[thread overview]
Message-ID: <CAEg67GkYqBsFYLm0dUM27BbkSuyADifYAiTU463MunBA+=QB9g@mail.gmail.com> (raw)
In-Reply-To: <20180430031653.GI1392@brightrain.aerifal.cx>

On Mon, Apr 30, 2018 at 1:16 PM, Rich Felker <dalias@libc.org> wrote:
> On Mon, Apr 30, 2018 at 12:52:06PM +1000, Patrick Oppenlander wrote:
>> - Is there a way that spinlocks could be disabled or bypassed on
>> uniprocessor systems?
>
> Whether locks are needed is a matter of whether there are multiple
> threads, not whether it's uniprocessor or multiprocessor. For some
> things where it's likely to matter (stdio, malloc, some other
> internals), locks are already optimized out when there is only one
> thread. In other cases it was deemed either too costly/difficult or
> irrelevant to overall performance.

I was talking about the case of a uniprocessor system running a multi
theaded process.

In that case the "spin" part of spinlock just burns time & electrons.
The "lock" part obviously can't be omitted. Calling straight through
to the kernel is the most efficient thing to do.

Patrick


  reply	other threads:[~2018-04-30  3:55 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-30  2:52 Patrick Oppenlander
2018-04-30  3:16 ` Rich Felker
2018-04-30  3:55   ` Patrick Oppenlander [this message]
2018-04-30 15:35     ` Rich Felker
2018-05-01  2:35       ` Patrick Oppenlander
2018-05-01 21:03         ` Rich Felker
2018-05-01 22:14           ` Patrick Oppenlander
2018-04-30  5:17   ` Patrick Oppenlander
2018-04-30 15:29     ` Rich Felker
2018-05-01  2:32       ` Patrick Oppenlander
2018-04-30  5:29   ` Patrick Oppenlander
2018-04-30 15:31     ` Rich Felker
2018-05-01  2:34       ` Patrick Oppenlander
2018-05-01 15:52         ` Rich Felker
2018-05-01 17:35           ` Rich Felker
2018-05-01 21:49             ` Andre McCurdy
2018-05-01 22:14               ` Szabolcs Nagy
2018-05-02 13:42                 ` Rich Felker
2018-05-01  0:10   ` Patrick Oppenlander
2018-05-01 14:19     ` Szabolcs Nagy
2018-05-01 21:05     ` Rich Felker

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