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From: Andi Kleen <ak@suse.de>
To: Andrew Morton <akpm@osdl.org>
Cc: Benjamin LaHaise <bcrl@kvack.org>,
	dada1@cosmosbay.com, kiran@scalex86.org, davem@davemloft.net,
	linux-kernel@vger.kernel.org, shai@scalex86.org,
	netdev@vger.kernel.org, pravins@calsoftinc.com,
	linux-arch@vger.kernel.org
Subject: Re: [patch 3/4] net: Percpufy frequently used variables -- proto.sockets_allocated
Date: Sun, 29 Jan 2006 06:38:17 +0100	[thread overview]
Message-ID: <200601290638.18630.ak@suse.de> (raw)
In-Reply-To: <20060128165549.262f2b90.akpm@osdl.org>

[adding linux-arch]

On Sunday 29 January 2006 01:55, Andrew Morton wrote:
> Benjamin LaHaise <bcrl@kvack.org> wrote:
> > On Sat, Jan 28, 2006 at 01:28:20AM +0100, Eric Dumazet wrote:
> > > We might use atomic_long_t only (and no spinlocks)
> > > Something like this ?
> >
> > Erk, complex and slow...  Try using local_t instead, which is
> > substantially cheaper on the P4 as it doesn't use the lock prefix and act
> > as a memory barrier.  See asm/local.h.
>
> local_t isn't much use until we get rid of asm-generic/local.h.  Bloaty,
> racy with nested interrupts.

It is just implemented wrong. It should use 
local_irq_save()/local_irq_restore() instead. But my bigger problem
with local_t is these few architectures (IA64, PPC64) who implement it 
with atomic_t. This means we can't replace local statistics counters
with local_t because it would be regression for them. I haven't done the
benchmarks yet, but I suspect both IA64 and PPC64 really should
just turn off interrupts.

-Andi

  parent reply	other threads:[~2006-01-29  5:38 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2006-01-26 18:56 [patch 0/4] net: Percpufy frequently used variables on struct proto Ravikiran G Thirumalai
2006-01-26 18:59 ` [patch 1/4] net: Percpufy frequently used variables -- add percpu_counter_mod_bh Ravikiran G Thirumalai
2006-01-26 19:02 ` [patch 2/4] net: Percpufy frequently used variables -- struct proto.memory_allocated Ravikiran G Thirumalai
2006-01-27  9:01   ` Eric Dumazet
2006-01-26 19:03 ` [patch 3/4] net: Percpufy frequently used variables -- proto.sockets_allocated Ravikiran G Thirumalai
2006-01-27  8:53   ` Eric Dumazet
2006-01-27 19:52     ` Ravikiran G Thirumalai
2006-01-27 20:16       ` Andrew Morton
2006-01-27 22:30         ` Eric Dumazet
2006-01-27 22:50           ` Ravikiran G Thirumalai
2006-01-27 23:21             ` Eric Dumazet
2006-01-28  0:40               ` Ravikiran G Thirumalai
2006-01-27 22:44         ` Ravikiran G Thirumalai
2006-01-27 22:58           ` Eric Dumazet
2006-01-27 23:16             ` Andrew Morton
2006-01-28  0:28               ` Eric Dumazet
2006-01-28  0:35                 ` Eric Dumazet
2006-01-28  4:52                   ` Ravikiran G Thirumalai
2006-01-28  7:19                     ` Eric Dumazet
2006-01-28  0:43                 ` Andrew Morton
2006-01-28  1:10                   ` Eric Dumazet
2006-01-28  1:18                     ` Andrew Morton
2006-01-29  0:44                 ` Benjamin LaHaise
2006-01-29  0:55                   ` Andrew Morton
2006-01-29  1:19                     ` Benjamin LaHaise
2006-01-29  1:29                       ` Andrew Morton
2006-01-29  1:45                       ` Kyle McMartin
2006-01-29  5:38                     ` Andi Kleen [this message]
2006-01-29  6:54                   ` Eric Dumazet
2006-01-29 19:52                     ` Benjamin LaHaise
2006-01-27 23:01           ` Andrew Morton
2006-01-27 23:08             ` Andrew Morton
2006-01-28  0:01               ` Ravikiran G Thirumalai
2006-01-28  0:26                 ` Andrew Morton
2006-02-03  3:05             ` Ravikiran G Thirumalai
2006-02-03  3:16               ` Andrew Morton
2006-02-03 19:37                 ` Ravikiran G Thirumalai
2006-02-03 20:13                   ` Andrew Morton
2006-01-26 19:05 ` [patch 4/4] net: Percpufy frequently used variables -- proto.inuse Ravikiran G Thirumalai

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