From: Al Viro <viro@ZenIV.linux.org.uk>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Tom Musta <tommusta@gmail.com>,
Peter Zijlstra <peterz@infradead.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-kernel@vger.kernel.org, Paul Mackerras <paulus@samba.org>,
Anton Blanchard <anton@samba.org>,
Scott Wood <scottwood@freescale.com>, Torsten Duwe <duwe@lst.de>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
linuxppc-dev@lists.ozlabs.org, Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH v2] powerpc ticket locks
Date: Tue, 11 Feb 2014 02:56:45 +0000 [thread overview]
Message-ID: <20140211025645.GJ18016@ZenIV.linux.org.uk> (raw)
In-Reply-To: <1392086660.3996.50.camel@pasglop>
On Tue, Feb 11, 2014 at 01:44:20PM +1100, Benjamin Herrenschmidt wrote:
> That leaves us with 32 bits to put the ref and the owner. The question
> is how big the ref really has to be and can we have a reasonable failure
> mode if it overflows ?
>
> If we limit ourselves to, for example, 16-bit for the ref in lockref,
> then we can have the second 32-bit split between the owner and the ref.
>
> If we limit ourselves to 4k CPUs, then we get 4 more bits of ref ...
>
> So the question is, is it reasonable to have the ref smaller than
> 32-bit...
Every time you open a file, you bump dentry refcount. Something like
libc or ld.so will be opened on just about every execve(), so I'd say
that 16 bits is far too low. If nothing else, 32 bits might be too
low on 64bit boxen...
next prev parent reply other threads:[~2014-02-11 2:57 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-07 16:58 [PATCH v2] powerpc ticket locks Torsten Duwe
2014-02-07 17:12 ` Peter Zijlstra
2014-02-07 17:55 ` Torsten Duwe
2014-02-10 3:10 ` Benjamin Herrenschmidt
2014-02-10 15:52 ` Torsten Duwe
2014-02-10 17:53 ` Peter Zijlstra
2014-02-11 2:44 ` Benjamin Herrenschmidt
2014-02-11 2:56 ` Al Viro [this message]
2014-02-11 3:38 ` Benjamin Herrenschmidt
2014-02-11 9:53 ` Raghavendra KT
2014-02-11 10:40 ` Torsten Duwe
2014-02-11 18:30 ` Scott Wood
2014-02-11 19:34 ` Benjamin Herrenschmidt
2014-02-11 9:39 ` Raghavendra KT
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