From: David Miller <davem@davemloft.net>
To: clameter@sgi.com
Cc: zippel@linux-m68k.org, ak@suse.de, linux-arch@vger.kernel.org
Subject: Re: Better local_t implementation needed
Date: Fri, 20 Apr 2007 21:45:34 -0700 (PDT) [thread overview]
Message-ID: <20070420.214534.35875646.davem@davemloft.net> (raw)
In-Reply-To: <Pine.LNX.4.64.0704201723010.13787@schroedinger.engr.sgi.com>
From: Christoph Lameter <clameter@sgi.com>
Date: Fri, 20 Apr 2007 17:25:16 -0700 (PDT)
> On Fri, 20 Apr 2007, David Miller wrote:
>
> > That's correct for hardware interrupts. It will, however, work for
> > soft interrupts and similar contexts.
>
> Is there really a significant gain? It seems that such logic would be more
> expensive than an atomic operation.
>
> local_t is saving atomic overhead right? It does no good for cacheline
> contention etc. Adding another int will increase cache footprint.
> Another rat hole?
We've been doing it for SNMP statistics in the networking for a long
time and I'm pretty sure it's better than an atomic at least on
sparc64 where the atomic is 40 cycles minimum on several processors.
I really don't want to start using local_t's all over the damn place
if they are implemented as atomics until they are proven to be faster
which I doubt they are on sparc64 for one.
next prev parent reply other threads:[~2007-04-21 4:45 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-04-20 10:56 Better local_t implementation needed Andi Kleen
2007-04-20 16:10 ` Christoph Lameter
2007-04-20 17:01 ` Andi Kleen
2007-04-20 17:05 ` Christoph Lameter
2007-04-20 18:31 ` Luck, Tony
2007-04-20 20:14 ` Andi Kleen
2007-04-20 20:27 ` Christoph Lameter
2007-04-20 21:25 ` Roman Zippel
2007-04-20 22:39 ` David Miller
2007-04-21 0:25 ` Christoph Lameter
2007-04-21 4:45 ` David Miller [this message]
[not found] <617E1C2C70743745A92448908E030B2A015F2392@scsmsx411.amr.corp.intel.com>
2007-04-20 20:38 ` Christoph Lameter
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