linux-kernel - Re: 2048 CPUs [was: Re: New filesystem for Linux]

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Date:	Sun, 12 Nov 2006 14:28:13 +0000
From:	Pavel Machek <pavel@....cz>
To:	Mikulas Patocka <mikulas@...ax.karlin.mff.cuni.cz>
Cc:	Albert Cahalan <acahalan@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: 2048 CPUs [was: Re: New filesystem for Linux]

Hi!

> >>You can't tell that CPUs behave exactly 
> >>probabilistically --- it may
> >>happen that one gets out of the wait loop always too 
> >>late.
> >
> >Well,  I don't need them to be _exactly_ 
> >probabilistical.
> >
> >Anyway, if you have 2048 CPUs... you can perhaps get 
> >some non-broken
> >ones.
> 
> No intel document guarantees you that if more CPUs 
> simultaneously execute locked cmpxchg in a loop that a 

If we are talking 2048 cpus, we are talking ia64.

> CPU will see compare success in a finite time. In fact, 
> CPUs can't guarantee this at all, because they don't 
> know that they're executing a spinlock --- for them its 
> just an instruction stream like anything else.

...even i386 has monitor/mwait these days.
							Pavel
-- 
Thanks for all the (sleeping) penguins.
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