From: Daniel Borkmann <dborkman@redhat.com>
To: David Laight <David.Laight@ACULAB.COM>
Cc: Cong Wang <cwang@twopensource.com>,
David Miller <davem@davemloft.net>,
netdev <netdev@vger.kernel.org>
Subject: Re: [PATCH net-next 3/3] packet: use percpu mmap tx frame pending refcount
Date: Mon, 13 Jan 2014 13:57:45 +0100 [thread overview]
Message-ID: <52D3E2C9.5060706@redhat.com> (raw)
In-Reply-To: <063D6719AE5E284EB5DD2968C1650D6D459065@AcuExch.aculab.com>
On 01/13/2014 12:58 PM, David Laight wrote:
> From: Daniel Borkmann
> ...
>> But I think I found a different problem with this idea. It could
>> happen with net devices as well, but probably less likely as there
>> might be a better distribution of hold/puts among CPUs. However,
>> for TX_RING, if we pin the process to a particular CPU, and since
>> the destructor is invoked through ksoftirqd, we could end up with
>> a misbalance and if the process runs long enough eventually
>> overflow for one particular CPU. We could work around that, but I
>> think it's not worth the effort.
>
> The sum will be 'correct' when summed across all the cpu even if
> one of the values has wrapped - provided all the arithmetic is
> unsigned and the variables all the same type.
You are right, sorry, too much coffee this morning, I missed that.
Then, imho, this should work.
next prev parent reply other threads:[~2014-01-13 12:57 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-12 16:22 [PATCH net-next 0/3] pf_packet updates Daniel Borkmann
2014-01-12 16:22 ` [PATCH net-next 1/3] packet: improve socket create/bind latency in some cases Daniel Borkmann
2014-01-12 16:22 ` [PATCH net-next 2/3] packet: don't unconditionally schedule() in case of MSG_DONTWAIT Daniel Borkmann
2014-01-12 16:22 ` [PATCH net-next 3/3] packet: use percpu mmap tx frame pending refcount Daniel Borkmann
2014-01-13 5:51 ` Cong Wang
2014-01-13 9:55 ` David Laight
2014-01-13 11:19 ` Daniel Borkmann
2014-01-13 11:58 ` David Laight
2014-01-13 12:57 ` Daniel Borkmann [this message]
2014-01-15 1:16 ` David Miller
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