From: Ben Hutchings <bhutchings@solarflare.com>
To: Stephen Hemminger <shemminger@vyatta.com>
Cc: "David S. Miller" <davem@davemloft.net>, netdev@vger.kernel.org
Subject: Re: [PATCH 3/9] veth: convert to 64 bit statistics
Date: Fri, 10 Jun 2011 17:34:19 +0100 [thread overview]
Message-ID: <1307723659.2815.9.camel@bwh-desktop> (raw)
In-Reply-To: <20110608202241.52ce68ae@nehalam.ftrdhcpuser.net>
On Wed, 2011-06-08 at 20:22 -0700, Stephen Hemminger wrote:
> On Thu, 09 Jun 2011 03:00:41 +0100
> Ben Hutchings <bhutchings@solarflare.com> wrote:
>
> > On Wed, 2011-06-08 at 17:53 -0700, Stephen Hemminger wrote:
> > > Not much change, device was already keeping per cpu statistics.
> > > Use recent 64 statistics interface.
> > [...]
> >
> > It's also going to need to use u64_stats_sync functions.
> >
> > Ben.
> >
>
> No veth is doing per-cpu update therefore the new code has the same guarantee
> as the old code.
Per-cpu statistics avoid the problem of races between writers without
using expensive atomic operations. They don't solve the problem of
races between writer and reader (on 32-bit systems).
For example, if veth_get_stats() races with a receive or transmit that
increments a value from 0x00000001ffffffff to 0x0000000200000000, it may
see the value as 0x00000002ffffffff.
Ben.
--
Ben Hutchings, Senior Software Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.
next prev parent reply other threads:[~2011-06-10 16:34 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-09 0:53 [PATCH 0/9] 64 bit statistics for VM and 10G drivers Stephen Hemminger
2011-06-09 0:53 ` [PATCH 1/9] vmxnet3: convert to 64 bit stats interface Stephen Hemminger
2011-06-09 5:17 ` [Pv-drivers] " Scott Goldman
2011-06-09 0:53 ` [PATCH 2/9] xen: " Stephen Hemminger
2011-06-09 1:56 ` Ben Hutchings
2011-06-14 21:07 ` Konrad Rzeszutek Wilk
2011-06-15 8:38 ` [Xen-devel] " Ian Campbell
2011-06-09 0:53 ` [PATCH 3/9] veth: convert to 64 bit statistics Stephen Hemminger
2011-06-09 2:00 ` Ben Hutchings
2011-06-09 3:22 ` Stephen Hemminger
2011-06-10 16:34 ` Ben Hutchings [this message]
2011-06-09 6:26 ` David Miller
2011-06-09 0:54 ` [PATCH 4/9] ifb: convert to 64 bit stats Stephen Hemminger
2011-06-09 3:29 ` Eric Dumazet
2011-06-09 3:32 ` Stephen Hemminger
2011-06-09 3:37 ` Eric Dumazet
2011-06-09 0:54 ` [PATCH 5/9] netxen: convert to 64 bit statistics Stephen Hemminger
2011-06-09 6:13 ` Amit Salecha
2011-06-09 6:27 ` David Miller
2011-06-09 0:54 ` [PATCH 6/9] enic: update to support 64 bit stats Stephen Hemminger
2011-06-09 6:27 ` David Miller
2011-06-09 17:43 ` roprabhu
2011-06-09 0:54 ` [PATCH 7/9] myricom: update to " Stephen Hemminger
2011-06-09 6:27 ` David Miller
2011-06-09 0:54 ` [PATCH 8/9] niu: support 64 bit stats interface Stephen Hemminger
2011-06-09 6:27 ` David Miller
2011-06-09 0:54 ` [PATCH 9/9] s2io: implement 64 bit stats Stephen Hemminger
2011-06-09 1:52 ` Ben Hutchings
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