Re: [patch] SMP alternatives

From: Linus Torvalds
Date: Wed Nov 23 2005 - 17:19:18 EST

On Wed, 23 Nov 2005, Daniel Jacobowitz wrote:
> I don't think I see the point. This would let you optimize for the
> "multi-threaded, but hasn't created any threads yet" or even
> "multi-threaded, but not right now" cases. But those really aren't the
> interesting case to optimize for - that's the equivalent of supporting
> CPU hotplug.


There is not a _single_ compiler that is multi-threaded, and I'd argue
that there probably never will be. It's pointless.

There's a _lot_ of really performance-sensitive stuff that will NEVER EVER
be threaded. You may run a hundred copies of them at the same time, but
every single copy will be single-threaded.

And this will optimize that case in a BIG way.

This is _not_ about "CPU hotplug". This is _not_ about "threaded apps
before they are threaded". This is all about the fact that serious
computation is done single-threaded, and anybody who thinks that
single-threading is going away is so totally out to lunch that it's not
even fun.

And yes, Sun will die. Single-thread performance matters a hell of a lot,
and any company that bets that it doesn't, is a failure.

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