netdev - Re: [PATCH net-next] net: percpu net

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20101008215604.GF2408@linux.vnet.ibm.com>
Date:	Fri, 8 Oct 2010 14:56:04 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Stephen Hemminger <shemminger@...tta.com>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next] net: percpu net_device refcount

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@...il.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
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html