From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Stephen Hemminger <shemminger@vyatta.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>,
David Miller <davem@davemloft.net>,
netdev <netdev@vger.kernel.org>
Subject: Re: [PATCH net-next] net: percpu net_device refcount
Date: Fri, 8 Oct 2010 14:56:04 -0700 [thread overview]
Message-ID: <20101008215604.GF2408@linux.vnet.ibm.com> (raw)
In-Reply-To: <20101007103051.63b5177c@nehalam>
On Thu, Oct 07, 2010 at 10:30:51AM -0700, Stephen Hemminger wrote:
> On Thu, 07 Oct 2010 19:12:35 +0200
> Eric Dumazet <eric.dumazet@gmail.com> wrote:
>
> > We tried very hard to remove all possible dev_hold()/dev_put() pairs in
> > network stack, using RCU conversions.
> >
> > There is still an unavoidable device refcount change for every dst we
> > create/destroy, and this can slow down some workloads (routers or some
> > app servers)
> >
> > We can switch to a percpu refcount implementation, now dynamic per_cpu
> > infrastructure is mature. On a 64 cpus machine, this consumes 256 bytes
> > per device.
>
> It makes sense, but what about 256 cores and 1024 Vlans?
> That adds up to 4M of memory which is might be noticeable.
I bet that systems that have 256 cores have >100GB of memory, at which
point 4MB is way down in the noise.
Thanx, Paul
next prev parent reply other threads:[~2010-10-08 21:56 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-07 17:12 [PATCH net-next] net: percpu net_device refcount Eric Dumazet
2010-10-07 17:30 ` Stephen Hemminger
2010-10-07 18:06 ` Eric Dumazet
2010-10-08 21:56 ` Paul E. McKenney [this message]
2010-10-09 6:23 ` Eric Dumazet
2010-10-09 16:58 ` Paul E. McKenney
2010-10-11 19:13 ` David Miller
2010-10-11 19:38 ` Eric Dumazet
2010-10-11 19:41 ` David Miller
2010-10-11 19:49 ` David Miller
2010-10-11 19:51 ` Eric Dumazet
2010-10-11 20:22 ` [PATCH net-next V3] " Eric Dumazet
2010-10-12 19:36 ` David Miller
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