From: Christoph Paasch <christoph.paasch@uclouvain.be>
To: David Miller <davem@davemloft.net>
Cc: eric.dumazet@gmail.com, netdev@vger.kernel.org
Subject: Re: [RFC net] tcp: metrics: Avoid duplicate entries with the same destination-IP
Date: Thu, 16 Jan 2014 00:21:33 +0100 [thread overview]
Message-ID: <20140115232133.GA4957@cpaasch-mac> (raw)
In-Reply-To: <20140115.121856.712581760900022040.davem@davemloft.net>
On 15/01/14 - 12:18:56, David Miller wrote:
> From: Eric Dumazet <eric.dumazet@gmail.com>
> Date: Mon, 13 Jan 2014 08:47:49 -0800
>
> > On Mon, 2014-01-13 at 16:25 +0100, Christoph Paasch wrote:
> >
> >> Another solution might be to leave tcp_get_metrics() as it is, and in
> >> tcpm_new do another call to __tcp_get_metrics() while holding the
> >> spin-lock. We would then check __tcp_get_metrics twice for new entries
> >> but we won't hold the spin-lock needlessly anymore.
> >
> > This is the only solution if you want to fix this.
> > Cost of lookup are the cache line misses.
> > Avoiding the spinlock is a must.
> >
> > The second 'lookup' is basically free, as the first one have populated
> > cpu caches.
>
> Indeed, taking the lock in tcp_get_metrics() is to be avoided at all
> costs.
Yes, I will send the updated patch tomorrow. Didn't yet had the time to send
it.
Christoph
prev parent reply other threads:[~2014-01-15 23:21 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-13 15:25 [RFC net] tcp: metrics: Avoid duplicate entries with the same destination-IP Christoph Paasch
2014-01-13 16:47 ` Eric Dumazet
2014-01-15 20:18 ` David Miller
2014-01-15 23:21 ` Christoph Paasch [this message]
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