From: Eric Dumazet <eric.dumazet@gmail.com>
To: Ben Greear <greearb@candelatech.com>
Cc: Stephen Hemminger <shemminger@vyatta.com>,
Rick Jones <rick.jones2@hp.com>, Tom Parkin <tparkin@katalix.com>,
netdev@vger.kernel.org, David.Laight@ACULAB.COM,
James Chapman <jchapman@katalix.com>
Subject: Re: [PATCH v2] l2tp: use per-cpu variables for u64_stats updates
Date: Wed, 27 Jun 2012 23:35:47 +0200 [thread overview]
Message-ID: <1340832947.26242.169.camel@edumazet-glaptop> (raw)
In-Reply-To: <4FEB7BB9.1080905@candelatech.com>
On Wed, 2012-06-27 at 14:31 -0700, Ben Greear wrote:
> For an example, see the VLAN code. rx-errors and tx-dropped are only 32-bit
> counters. Now, in the real world, we wouldn't expect those counters to
> increase at high rates, but they are still 32-bit counters masquerading
> as 64, and they could wrap after a while, so any code that expected a wrap
> to mean a 64-bit wrap would be wrong.
>
> At the time I was last complaining, there were lots more cases
> of this that I was fighting with, but I don't recall exactly what they
> were. Once my user-space code got paranoid enough, it was able to
> at least mostly deal with 32 and 64 wraps.
Good, you now know how to deal correctly with these things.
Using 64bit fields for tx_dropped is what I call kernel bloat.
If only all drops were correctly accounted...
I believe 50% of drivers are buggy in this aspect.
next prev parent reply other threads:[~2012-06-27 21:35 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-27 12:00 [PATCH v2] l2tp: use per-cpu variables for u64_stats updates Tom Parkin
2012-06-27 19:03 ` Eric Dumazet
2012-06-27 20:21 ` Rick Jones
2012-06-27 20:39 ` Eric Dumazet
2012-06-27 20:50 ` Stephen Hemminger
2012-06-27 20:58 ` Ben Greear
2012-06-27 21:20 ` Eric Dumazet
2012-06-27 21:31 ` Ben Greear
2012-06-27 21:35 ` Eric Dumazet [this message]
2012-06-27 23:01 ` Rick Jones
2012-06-27 23:09 ` David Miller
2012-06-27 23:39 ` Rick Jones
2012-06-28 5:00 ` Eric Dumazet
2012-06-28 8:24 ` Tom Parkin
2012-06-28 8:46 ` David Laight
2012-06-28 18:17 ` Ben Hutchings
2012-06-27 21:32 ` Eric Dumazet
2012-06-27 21:40 ` Ben Greear
2012-06-27 21:50 ` Eric Dumazet
2012-06-27 21:00 ` Rick Jones
2012-06-27 22:21 ` David Miller
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